The proteins, free fatty acids and glycogen contents of freshly laid eggs of Amblyomma variegatum (F.) and Boophilus decoloratus (Koch) were estimated, using batches of eggs deposited sequentially over the full span of the oviposition period. The mean protein contents decreased from over 500 and 180 andmu; g/mg egg for the 2 species, respectively, in the early egg-batches, to less than 250 and 125 andmu; g/mg egg, respectively, in the later batches, but subsequently rose to over 400 and 230 andmu; g/mg egg in the final egg-batches. The mean fatty-acid components of eggs of both species rapidly declined from 310 and 380 andmu; g/mg, respectively, in the early batches to less than 75 and 90 andmu; g/mg egg in the final batches. The estimated glycogen contents showed a similar trend, beginning at 1.78-1.8 and 0.94-1.03 andmu; g/mg egg in the 2 species, respectively, and falling to almost zero in the last batches of eggs produced by females of both species. The factors responsible for the differential depletion rates or patterns of the various egg components are considered, and their possible implications in terms of the development and hatching rate of young ticks generally are discussed.