Purpose: Diode lasers present some advantages over the other surgical lasers. The equipments are more compact and can also be used in low intensity laser therapy. The aim of this study is to analyze a possible biostimulatory effect of the diode laser on human cultured gingival fibroblasts. Material and Methods: The celll ine FMM1 was grown in Dulbecco' modified Eagle medium. Laser irradiation was carried out with a GaAIAs diode laser (wavelength: 808 nm, power output: 3.5 W, Zap Lasers, CA, USA). The irradiation was done in a defocused and continuous wave mode using a fiber of 400 micrometers. The experiments were done in triplicate (Group 1: non-irradiated cells; Group 2: cells irradiated with 3 J/cm2; and Group 3: cells irradiated with 4 J/cm2). The data of the growth curves were analyzed by statistical means. Results and Conclusion: The defocused diode laser irradiation used as low intensity laser therapy presents biostimulatory effect on growth of human gingival fibroblasts.