Two types of salivary alveoli are present in adult Argas (Persicargas) persicus: agranular type I and granular type II alveoli. Type I alveoli consist of a large central cell surrounded by a constrictor cell and peripheral cells with numerous infoldings of the basal membrane similar to epithelia involved in active transport. The basal infoldings form a previously undescribed successively convoluted membraneous pattern which may increase the capability of peripheral cells for active transport. Type II alveoli consist of three granular cells (a,b,c) and two agranular (adlumenal and ablumenal interstitial) cells. Golgi bodies and rough endoplasmic reticulum are probably involved in the granule formation. The granules are discharged within 5-10 min after feeding commences, and presumably contain anticoagulant substances and pharmacologically active agents that promote the blood flow of the host during tick feeding. Although the adlumenal cells are not structurally affected by feeding, ablumenal cells develop into transport epithelia.