Interactions between polystyrene sodium sulfonate and insulin-secreting RINm5F cells have been previously described. When cultured on these microcarriers, cells exhibited normal growth, altered morphology, and inhibition of the insulin secretion was observed. For the sake of comparison, interactions of RINm5F cells with Sephadex derivatives, namely, carboxymethyl Sephadex (CM Seph), benzylaminated CM Seph(CMB Seph), and sulfonated CMB Seph (CMBS Seph), as well Sephadex, were studied. Cells attached poorly and did not spread onto Sephadex and CM Seph microcarriers, but all other characteristics were normal. In contrast, with cells cul-tured on CMB Seph and CMBS Seph microcarriers cell attachment, morphology, and growth rate were comparable to those of cells grown on classic plastic wells. But, in the latter case, surprisingly, insulin secretion was enhanced. This effect is composition of the microcarriers dependent. The insulin secretion per cell-microcarriers composition relationship suggests a specific interaction between an unknown membrane receptor of RINm5F cells and a composite ligand site made of a combination of different chemical functional groups present at the microcarriers surface.