Salivary glands of the unfed adult Argas (Persicargas) arboreus (family Argasidae) contain 2 types of alveoli, one nongranular and one granule-secreting. The fine structure of the nongranular alveolus is similar to that of the family Ixodidae. In the granule-secreting alveolus, the presence of 3 types of secretory cells, each with morphologically distinct granular inclusions, confirms histological and histochemical observations on argasid salivary glands. Epithelial cells with numerous membranous infoldings, mitochondria, microtubules, and a complex canalicular system probably concerned with fluid regulation and secretion are located between granule-secreting cells and form caps over their basal regions. The luminal border of both secretory and epithelial cells is microvillate. The alveolar lumen leads into the chitinous alveolar duct which lacks the complex valvular structure of ixodid alveoli. Axons containing neurosecretory material occur in both nongranular and granule-secreting alveoli and probably control salivary secretion.