Acetonitrile has been shown to be a better dehydrating agent than ethanol for whole tissue prepared for TEM studies. In this paper we show that it is also a better choice for dehydration of cell cultures prepared for SEM studies. The procedures used for the isolation and culture of cardiac cells in the present study have been outlined in detail by Schroedl and Hartzell (1983) and Freerksen, et al. (1984). Cells were cultured in suspension using HARV-Bioreactors (Synthecon, Inc., Friendswood, TX) for 24 hours to allow attachment and then fed each subsequent 48 hours. After a total of six days in suspension culture, cell/bead clusters were collected and washed with PBS.Primary fixation was done at 4°C, all other steps were performed at room temperature. The buffer used in all cases was 0.1M cacodylate, pH 7.3. The cell/bead cultures were processed according to the following protocol. All of the beads were placed in a 1.5 ml microfuge tube and fixed in 2% buffered glutaraldehyde overnight followed by two 5 min washes in buffer, postfixation in 1% buffered OsO4 for 90 min and three washes in buffer. One half of the beads were then placed in another microfuge tube and dehydrated in acetonitrile, while the remaining beads were dehydrated in ethanol.