We investigated the effects of age, sex and strain in the induction of peritoneal exudate colony‐forming cells (PE‐CFC) in mice. Sex and age (ranging from 3 weeks to 12 months) had no significant effect on the induction of PE‐CFC. However, we found significant difference between strains in terms of the number of nucleated cells and the proportion of PE‐CFC in exudate cells. When we investigated the mechanisms behind this strain difference, we found that it was due to neither the type of colony‐stimulating factor employed in culture, nor the type of stimulants used to induce the exudate, nor the difference in the kinetics of appearance of PE‐CFC in the peritoneal cavity. We also studied the induction of PE‐CFC in rats and hamsters and the growth of these cells in vitro. Unlike mouse cells, PE‐CFC from rats and hamsters could also use media conditioned by cells from other species as a source of colony‐stimulating factor.