Physical therapy is one of the most ancient methods of medical treatment. Historically such factors as air, sun and water were used everywhere, then, gradually, with the deeping knowledge about environment and world this arsenal grew. In addition to natural, artificial action sources, electrical and electromagnetic fields, optical radiation, mechanical and temperature factors have come into use.

The discovery in 60-s of the possibility of intensify light by stimulated radiation results in the creation of lasers, which found immediate application in medicine. In 1974 the Ministry of Medical Care of the USSR gave permission for clinical use of the first device for laser therapy. So the Low Level Laser Therapy (LLLT) is one of the latest developments of the phototherapy. During the last 20 years laser therapy has received wide recognition in medical practice and has occupied a stable important position among the medical physical factors used before.

The range of laser applications is so wide that sometimes the question of separation of this method into an independent branch of medical science arises. If up to mid 80-s red HeNe laser (632.8 nm) was actively studied and used in clinical practice, during the last ten years, red (630 - 670 nm) and infrared (830 - 1300 nm) laser diodes have been widely applied, which is explained by their small size, simple maintenance, long service life, economy and rather high clinical efficiency. Blue and ultraviolet lasers find their application too, especially for fighting infections.

Low level laser blood irradiation (LBI) is one of the most perspective methods of low level laser therapy. LBI is used in the therapy of several disorders. LBI had several positive effects, such as antiinflammatory effect, activation of immune system, protection of vessels, improvement of blood microcirculation and tissue trophic processes, activation of regeneration and reparation (Sirenko et al. 1992). Better state of vascular wall, atherosclerotic plaque size reduction, improvement in blood microcirculation were observed among patients with atherosclerotic vascular disease after transcutaneous infrared (IR) LBI (Kaplan et al. 1997).

Some scientists considered as a key importance problem determination the most appropriate methods of applying laser energy, dosage. In the same time some Russian scientists (Karu, Drill, Klebanov) considered as the most important factor the wavelength of light and main photo-acceptor molecule or structure. They argued that laser light and non-coherent light of same wavelength and power density have the same biological and medical effects.

It was shown that different spectra light have approximately the same influence on then organism. For example, Samojlova (1998) compared results of photo-modification of blood under HeNe intravenous and UV extra-corporate irradiation. She reported that changes in blood cells after UV irradiation were very close but not completely similar to changes discovered after HeNe blood irradiation. Other scientists reported that the clinical effects of HeNe and IR laser irradiation are also the some.

Kapustina (1997) reported that 3 main groups of patients according to the response to LBI were detected. The first group patients had immediate in vitro (within 15 min.) positive changes in the state of erythrocyte membranes under LBI, the second group patients had postponed response, and the third group patients had no response at all. Clinical (in vivo) studies proved, that the first group patients showed better and faster treatment results. For the second group patients more sessions of LBI were required to achieve therapeutic results. No therapeutic effects were discovered for group 3 patients.

Several studies emphasized that laser effects were detected in the case of irradiation of damaged cells and organisms. In the case of irradiation of normal and healthy organisms very slight or no changes at all were registered.

The influence of low level laser irradiation on the organism has several clinical effects, including anti-inflammatory, immune stimulating, neurotrophic, analgesic, desensitizing, bactericidal, antiedemic, normalizing the blood rheology and hemodynamics effects. So the areas of application of LLLT are very large and include almost all branches of medicine:
Cardiology - ischemic heart disease, stenocardia, myocardial infarction;
Otorhinolaryngology - pharyngitis, tonsillitis, maxillary sinusitis, tracheitis, otitis;
Gastroenterology - gastritis, stomach ulcer and duodenal ulcer, cholecystitis, pancreatitis, hepatitis, colitis;
Dermatology - dermatitis, dermatosis, neurodermite;
Pulmonary diseases - bronchial asthma, pneumonia, pleuritis;
Gynecology - mastitis, inflammations, erosions, generic and postnatal complications;
Urology - adenoma, prostatitis, cystitis, urethritis, nephritis, pyelonephritis, urolithic disease;
Proctology - hemorrhoids, periproctitis, anal pruritus and fissures;
Neuropathology - neuritis of upper and lower extremities, radiculitis, neuralgia of the head and face;
Arthrology - diseases of joints and vertebral column;
Stomatology - caries, pulpitis, periodontitis, paradontitis.

In the near future more studies about the influence of different wavelength laser light on the organism, the most appropriate dosage of laser irradiation would be done. As a result probably the mechanisms of laser therapy would be more understandable, as well as the methods of forecasting the clinical effects of laser irradiation would be development.