The aim of this study was to analyze the influence of non-surgical applications of diode laser (940 nm) on the cell proliferation and mRNA expressions of type I collagen and growth factors in human gingival fibroblasts (GF) . Gingival fibroblasts were isolated from human gingival connective tissue of systemically healthy individuals. Cells were treated with different laser parameters as follows; (1) Infected pocket setting (powEr:2 W, pulse interval: 1 ms, pulse length: 1 ms, 20 s/cm2) ; (2) Perio-pocket setting (powEr:1.5 W, pulse interval: 20 ms, pulse length: 20 ms, 20 s/cm2) ; and (3) Biostimulation setting (powEr:0.3 W in continuous wave, 20 s/cm 2) . Proliferation of GF was evaluated after different laser applications using a real-time cell analyzer. Total RNA was isolated on day 2 and cDNA synthesis was performed. Type I collagen, insulin-like growth factor (IGF), vascular endothelial growth factor (VEGF) and transforming growth factor-beta (TGF-β) mRNA expressions were determined with quantitative RT-PCR. In a proliferation experiment, no significant differences were observed in the different laser applications when compared to the control group. Statistically significant increases in IGF, VEGF, and TGF-β mRNA expressions were noted in the laser groups when compared to the untreated control group (p<0.05) . A significant increase in collagen type I mRNA expression was noted in only biostimulation set-up of diode laser (p<0.05) . The results of this study demonstrate that non-surgical laser applications modulate behavior of gingival fibroblasts inducing growth factors mRNA expressions and these applications can be used to improve periodontal wound healing. © 2010 Springer-Verlag London Ltd.