A cw 1.48 micrometers diode-laser microsurgical procedure is investigated allowing drilling of mouse zona pellucida without micromanipulators or handling of the egg outside the culture dish. The laser beam (60 - 70 mW at the focal point) and a coaxial red light aiming laser are directed through the objective (45 X) of an inverted microscope and focused in spots of 2 - 3 micrometers diameter. Mice zygotes are suspended in groups of 15 - 20 (Nunc culture dishes) in 1 ml culture medium. Egg zona is positioned with the microscope stage on the control spot and exposed to laser light (10 - 20 ms; 0.65 - 1.3 mJ). One laser pulse is sufficient to drill openings ranging from 5 - 7 micrometers diameter depending on laser power and exposure time. Drilled zygotes (N equals 150) develop to the blastocysts stage at a rate (70%) comparable to the control. There is no evidence of thermal damage under optical microscopic observation. In conclusion, the 1.48 micrometers laser radiation allows us to drill holes in mouse zona pellucida in a rapid, simple and non touch procedure. Its high absorption by water and non-mutagenicity makes it a useful tool for assisted fertilization procedures.