Human adrenal cortical tumor cells (SW-13) grow into a typical epithelial cell monolayer when seeded onto culture dishes. The cells of the SW-13 population monolayer appear flattened with few conspicuous surface features. The cells are attached to one another at their lateral borders and are arranged in a cobblestone-like manner. Following Triton X-100 extraction, the distribution of the cytoskeletal elements was observed with scanning electron microscopic techniques to correspond to the shape of the non-extracted cell. Changes in the distribution and morphology of projections on the cell surface as well as changes in cell shape were revealed after treatment of the cultures with compounds which bring about microtubular and microfilament disruption. Following 60 minute treatment of the cell population with cytochalasin B (10 micrograms/ml), 90% of the cells became round while remaining attached to neighboring cells and to the substrate by slender cell processes and filopodia. Some bleeding could be seen on the cell surfaces of cytochalasin B treated cultures and an increase in the number of microvilli was evident. When the cytoskeletal elements were observed with scanning electron microscopic techniques after Triton X-100 extraction, the amount of peripheral cytoskeletal elements was decreased and only slender projections of the microfilaments and microtubules were evident. Colchicine (0.06 micrograms/ml) treatment of the SW-13 adrenal cell population resulted in the appearance of surface blebs within 10 minutes of the initiation of treatment. The changes in surface projections are discussed in relationship to the loss of microtubules and microfilaments from the cytoplasm of the cell.