The salivary system of the Vespidae consists of mandibular, hypopharyngeal and salivary (thoracic) glands. Thoracic salivary glands are related to the foraging activities, adult-adult and adult-larvae trophalaxis, larval feeding and nest construction. The study of these glands is important to understand the mechanisms of secretion and their relation with behavioral habits. In this report we describe the ultrastructure of the thoracic salivary glands of adult Polistes versicolor. The glands were excised from anesthetized specimens and fixed in 2.5% glutaraldehyde in 0.1 M sodium cacodylate, pH 7.2, post-fixed in 1% OsO4 in the same buffer and dehydrated in ethanol series. Transmission electron microscopy showed that the thoracic salivary glands had a secretory portion consisting of pseudoacini. Each pseudoacinose secretory unit included a central cell (TA) surrounded by several parietal cells (TB). From these pseudoacini, canaliculi arose and fused to form the main ducts (ducts 1, 2 and 3 of increasing diameter). The duct system was formed by epithelial type C (TC) cells, but lacked a reservoir. Type D (TD) cells occurred near the base of duct 2. These findings indicate that P. versicolor thoracic salivary glands consist of several cell types that have specific roles in secretion biosynthesis (TA), modification (TB, TC, TD) and transport (TC).