Three types of salivary alveoli are present in the female Hyalomma ( Hyalomma) dromedarii, agranular alveolus 1 and granular alveoli II and III. In males there is an additional granular alveolus, type IV. Type 1 alveoli consist of a large central cell surrounded by 5-6 peripheral cells with numerous basal membrane infoldings similar to transporting epithelia. Each type of granular alveolus is composed of granular and agranular cells. In the female, 8 granular ccli types are recognized and 9 in the male. Three probably secrete cement required for firm attachment to the host and four others possibly function to secrete pharmacologically active agents to ens ure constant supply of blood to the feeding tick. Two granular cell types, h and i (the latter being present only in males) are of unknown function. The nagranular cells are the adlumenal and the ablumenal cells. The latter develop during feeding particularly in the female type III alveolus to be involved in ion and water transport. Comparative ultrastructure changes between the different salivary alveoli of the female and male are discussed.