A virginal, captive raised female Python molurus bivittatus, 347 cm long and weighing 29 kg, mated with a 297 cm, 14.5 kg male. About 114 days after mating, 35 eggs were laid, 34 of which were fertile. The female remained coiled around the eggs for 56 days until they hatched. Intermittent contractions of her body began several hours prior to egg laying and stopped the day after the eggs hatched. Three weeks prior to egg laying, the mean body temperature of the snake was 3.1°C higher than that of the substratum. For 46 days after the eggs were laid, the body temperature increased further to 33-33.5°C in the morning and 34-34.5°C in the evening for 46 days with a mean body-substrate temperature differential of 6.2°C. During the last ten days of incubation, the body temperature gradually decreased and reached the normal level of slightly above ambient temperature at the time the eggs hatched. Four of the eggs were removed immediately after laying. Two of these contained 8.3 cm long, living embryos. The other two were incubated artificially at 33.5-34.5°C and 95% relative humidity. One of these was opened after 25 days incubation yielding a fetus 28.9 cm long that weighed 17.8 gm. The fourth egg hatched at the same time as those incubated by the female. One of the naturally incubated eggs was opened at 47 days and contained a fetus which was 58 cm long and weighed 100.5 gm. Two fetuses died near term, and two hatchlings had congenital anomalies. Normal young, hatched from the remaining 27 eggs, had an average length of 72 cm and an average weight of 125.5 gm after the first shed.