Aedes aegypti were infected with chikungunya virus by being fed on a blood–virus suspension poured over a sugar cube. The virus infection in the salivary glands was then studied with the electron microscope. In the proximal portion of the lateral lobes, 250–310 Å virus precursor particles were seen in the nucleus, in the cytoplasm, and on the membranes of cytoplasmic vesicles. Enveloped 500–580 Å virus particles with a 250–310 Å core were seen within the vesicles, in intercellular spaces, and in large numbers in the apical cavity and periductal space. In the distal portions of the lateral and median lobes precursor particles were present in the nucleus and cytoplasm, but no cytoplasmic vesicles were seen. Numerous enveloped virus particles were seen in the apical cavity and periductal space, and in the median lobe within the duct lumen as well. No evidence of virus replication was seen in the intermediate portion of the median lobe.In the distal portions, virus particles were frequently associated with a concentration of the secretory material. No other microscopically visible pathological changes were seen in the infected salivary glands.