Scanning electron microscopy of the epithelial cells of the female hamster harderian gland reveals a range of surface features. Some cells exhibit a uniform covering of microvilli while others, often with swollen apices, are relatively devoid of microvilli. Surface pitting is frequent for all cells; pits represent regions of exocytotic lipid vacuole release. A similar range of surface appearances occurs in the male gland but here cells with uniform microvilli represent type I cells (characterised by small lipid vacuoles) while swollen cells with sparse microvilli are type II cells (characterised by large lipid vacuoles). It is suggested that different cell forms represent a single cell type in varying activity states. Luminal debris is often marked, consisting chiefly of lipids. Solid porphyrin accretions, sometimes surrounded by neutrophils, are numerous in female (but not male) glands. Interstitial mast cells are also numerous in the female gland. The gland contains fenestrated capillaries and extensive lymphatics. The duct of the gland, which has received little attention, possesses ciliated cells, nonciliated cells and basal cells. Ciliated cells possess kinocilia and relatively tall thin microvilli, as well as some lipid vacuoles. Nonciliated cells bear shorter microvilli, apically located mucoid granules, and lamellar formations of smooth endoplasmic reticulum. The basal cells are squat and pyramidal; their lateral walls, which interdigitate with the main duct cell types, show pronounced folding.