Micromanipulation of mouse gametes with a commercially available compact laser microbeam system was studied. Both the normal in-vitro fertilization (IVF) group and the laser zona dissection (LZD) group were tested under normal (2 x 10(6) motile spermatozoa/ml) and low (500,000 motile spermatozoa/ml) insemination conditions. Subzonal insemination (SUZI) was also tried in a small group of gametes and the results were compared with those of the low insemination groups. Fertilization rates and blastocyst formation rates for the IVF and the LZD-treated groups were respectively 53 and 60% and 60 and 78%, which were not significantly different. However, under low insemination conditions, the results were significantly better in the LZD-treated group (58% fertilization rate and 83% blastocyst formation rate) compared to the results of the IVF group (33 and 48%) (P < 0.05). The SUZI-treated group showed the lowest fertilization rate (18%). No significant difference between the LZD and the IVF group was observed with respect to parthenogenetic activation. LZD has a beneficial effect on fertilization rates in cases of reduced sperm quality.