Objective: The aim of this study was to determine the optimum operating parameters (pulse duration, energy levels, and application time) to promote induction of osteoblast and fibroblast cell proliferation and to maintain cell viability treated with low-intensity pulsed ultrasound (LIPUS) and low-level laser therapy (LLLT). Background data: The positive effects of LIPUS and LLLT on cellular activity have been reported in recent years. Comparisons between experimental parameters of previous studies are difficult because scientific studies reported frequencies and the duty cycles of LIPUS and wavelengths and doses of LLLT in a wide range of parameters. However, optimum amount of energy and optimum time exposure must be determined to induce bone and tissue cell proliferation for effective healing process and to avoid cell damage. Material and methods: Fibroblast and osteoblast cell cultures were irradiated with LIPUS (10-50% pulse and continuous mode at 1 and 3MHz for 1, 3, and 5min) and LLLT (4, 8, and 16J at 50, 100, 200, 300, 400, and 500mW). Cell cultures were analyzed using XTT assay. Results: For both cell types, LIPUS treatment with 10% pulse (1:9 duty cycle), 3MHz, and for 1min and LLLT treatment over 100mV for 4, 8, and 16J modalities contributed to the growth, and may help bone repair and tissue healing process optimally. Conclusions: Bio-stimulating effects of LLLT irradiation promote proliferation and maintain cell viability better than LIPUS treatment without causing thermal response for both cell types, and the therapeutic modality above 200mV has maximum effectiveness.