In order to study the influence of cell shape as modulated by the extracellular matrix on the cellular activity, hepatocytes isolated from liver were maintained on collagen I coated plastic substrata and collagen I gel substrata and certain hepatocyte specific functions were investigated. The incorporation of 3[H]-leucine into total proteins and albumin secreted by cells maintained on collagen gel was found to be significantly higher compared to those maintained on a collagen coated plastic substrata, indicating that hepatocytes on collagen gel have an enhanced albumin synthesizing capacity. Increased incorporation of 35[S]-sulphate into total proteoglycans (PG) and a relatively higher fraction of the 35[S]-PG in the extracellular space showed an increased rate of synthesis and secretion of sulphated PGs by cells on collagen gels. But in contrast to the above results, the incorporation of 3[H]-leucine into cytokeratins C8, C18 and actin were significantly low in cells maintained on collagen gel. The tyrosine amino transferase activity exhibited by hepatocytes preincubated with dexamethasone on collagen gel was also significantly low. The different forms of collagen substrata appeared to have no effect on the amino acid transport by hepatocytes, further suggesting that the various hepatocyte specific functions are not uniformly altered when hepatocytes are maintained on three-dimensional collagen gel substrata. These results indicate that the shape of the cell as determined by the nature of the matrix substratum influences the synthetic activity of secretory proteins and those remaining intracellularly, differently.