Plasmodium ookinetes secrete chitinases to penetrate the acellular, chitin-containing peritrophic matrix of the mosquito midgut en route to invasion of the epithelium. Chitinases are potentially targets that can be used to block malaria transmission. We demonstrate here that chitinases of Plasmodium falciparum and P. gallinaceum are concentrated at the apical end of ookinetes. The chitinase PgCHT1 of P. gallinaceum is present within ookinete micronemes and subsequently becomes localized in the electron-dense area of the apical complex. These observations suggest a pathway by which ookinetes secrete proteins extracellularly.