Salivary glands of female Anopheles stephensi Liston have been found to consist of three glandular regions, i.e. the proximal and distal portions of lateral lobes, and the distal portion of the median lobe; and of two non-glandular regions, the intermediate portions of the lateral and median lobes. Secretory material which appears as large secretion masses in whole glands is entirely extracellular. From the manner of preservation of this secretory material, it is suggested that that of the distal portion of the median lobe is present in the most concentrated, or least hydrated form, while that of the proximal portions of the lateral lobes is present in the least concentrated, or most hydrated form. As the cellular anatomy of the intermediate portions shows membrane developments similar to those found in other cells that are concerned with water transport, it is suggested that these intermediate portions function to dilute the concentrated secretions of the more distal portions. Variations in endoplasmic reticulum and ribosome distribution and in nuclear morphology of the cells of the proximal portions of the lateral lobes suggest that these cells have a continuous cycle of secretory activity.