Hybridoma cells (S3H5/γ2bA2) are found to grow either in suspension or as attached to the surface of cell culture T flask. Cell growth rates and monoclonal antibody (MAB) production rates of both suspended and attached cells were examined. Although the percentage of viable cells was higher for the attached cells, cells growing in suspension showed almost the same charateristics as cells attached to the flasks with respect to cell growth and MAB production rate. Cell attachment increased with increasing serum concentrations up to 5% and remained essentially constant at cell densities of about 2·105/cm2. No differences in cell growth rate and MAB production could be attributed to anchorage dependent growth.