Egg production by females of Boophilus microplus (Can.) was shown to be proportional to initial weight of the females; small ticks were found to be less efficient in producing eggs than ticks in the optimal weight range of 160-300 mg. The duration of the oviposition period varied with temperature, the peak occurring early in the cycle. Eggs laid at the beginning and end of the oviposition period (10% of the total) took longer to hatch and were not as viable as eggs laid during the peak. The length and breadth of the eggs did not vary markedly throughout the oviposition period but the weight decreased towards the end of the cycle.