The aim of this study is to investigate. The effects exerted by using helium: neon He:Ne laser (632.8 nm) low level laser irradiation (LLLI) on neutrophil activity in response to opsonized zymosan. Human buffy coat leukocytes primed with opsonized zymosan were exposed to 10 mw He:Ne laser at energy densities of 1-5 J/cm². Phagocytic activity was assessed by measuring percent of phagocytosis, (hydrogen peroxide) H2O2 and nitric oxide (NO) generation together with neutrophil-associated nitric oxide synthetase activity. Irradiation with low intensity red light stimulated neutrophil, an effect which was intensified, when neutrophils were dually stimulated by LLLI and opsonized zymosan within the dose range of 3-5 with maximum activity at 5 J/cm².