Abstract The cytotoxic effects of various prolamin-derived peptides on Caco-2 cells were investigated by measuring the alterations of several parameters at different stages of cell differentiation. The PT digest of bread wheat was active in inhibiting cell proliferation (by about 50%), whereas the other digests from durum wheat, maize and bovine serum albumin (BSA) did not affect the proliferating activity of cells. Compared with the control, colony-forming ability was inhibited by 20% by treatment with cereals that are toxic in coeliac disease (bread wheat, rye, oats and barley). BSA and maize peptides are devoid of this in vitro effect. However, the decrease in alkaline phosphatase activity during Caco-2 cell differentiation was observed in the presence of bread wheat. This could be due to slowing down of the enterocytic differentiation of cells that are susceptible to interaction with toxic peptides. Therefore, long-term cultures of Caco-2 cells constitute a useful in vitro model to assess the ability of cereal proteins to damage the coeliac small intestine.