The eggs of nine of the commoner Costa Rican anophelines were studied. Four had been known previously from reports published from other countries. The remaining five species, the eggs of which are here described for the first time, include Anopheles anomalophyllus, A. apicimacula, A. neomaculipalpus, A. punctimacula and A. vestitipennis. About thirty photomicrographs were taken of dorsal, lateral and ventral views of ova and nearly fourteen hundred eggs were measured. The longest eggs were those of A. neomaculipalpus and A. vestitipennis, the shortest those of A. strodei. There was no evidence that the eggs of A. albimanus laid at the beginning of the dry season were any larger than those deposited during the preceding rainy months. Variations were found in the ova secured from A. punctimacula and A. vestitipennis. Such variations occurred at times in a batch of eggs laid by a single female mosquito. The real significance of the different types of eggs laid by apparently identical female anophelines is not yet clear, though it is possible that these variations may be seasonal like the A. walkeri observed by Hurlbut.