Macrophages are a source of many important mediators of wound repair. Cells of a established macrophage-like cell line (U-937) were exposed in vitro to a 820 nm coherent light source, (Omega Laser Systems) at the following frequencies: 2.28, 18.24, 292.3 and 1000 Hz. The average power output was 50 mW and the irradiation times were such that the energy density to which the cells were exposed was kept constant at 7.2 J/cm². 12 hours later the macrophage-conditioned medium was removed and placed on 3T3 fibroblast monolayers. Fibroblast proliferation was assessed over a five day period. Five days after the addition of the medium conditioned by macrophages exposed to a energy density of 7.2 J/cm², there was a statistically significant increase in fibroblast proliferation in the groups treated with laser at frequencies of 2.28, 18.24 and 292.30 Hz in comparison with the sham-irradiated controls. Treatment at the 1000 Hz frequency was followed by less proliferative activity than in the controls, although this was not statistically significant.