Bacteriophage state currently an attractive alternative for antibiotics, especially due to the strong in vitro activity and lack of side effects. Eight patients with chronic infection in musculoskeletal system.are presented This group includes: 3 cases of deep periprosthetic infection, posttraumatic osteomyelitis of tibia in 2 cases, infected pseudoarthrosis of femur in 1 case, chronic hematogenous osteomyelitis of tibia in 1 case, chronic infection in diabetic foot in 1 case. Adequate tissue specimen for bacteriology was taken during operation and selection of bacteria strains was subsequently done and appropriate phage were cultured. Phage were taken orally by patients 4–6 weeks after operation. Despite of paralel phage and systemic antibiotic administration all patients underwent operative debridement of infected bone. Simultaneously, every 7 days parameters of immunological response was measured in peripheral blood. They were: lymphocyte B activity (PFC and SAC test), lymphocyte T (NK) activity and phagocytose stimulation (PMA 30 test). There was a two-fold increase of lymphocyte B activity in PFC test with peak on day 7 after phage administration. Additionally slightly increase of NK cells and phagocytic activity and both increase and decrease of lymphocyte B and T activity in SAC test was observed. Eventually remission of infection was achieved in 6 from 8 patients. It is difficult to state a correlation between in vitro bactericidal effect of bacteriophage, immunological stimulation in peripheral blood and clinical results achieved after both operative and antimicrobial therapy.