The objective of the present study was to determine the distribution of insulin-like growth factor (IGF-I) receptors in all layers of the adult rat intestine and differences among the parts of the intestine. Immunohistochemical method to paraffin sections was applied to define the cellular distribution of IGF-I receptors. Receptor staining intensity decreased from proximal to distal intestine. A greater density of the reaction both in the apical region of the villi and in the crypt epithelium of the small intestine was found. The staining was remarkably less in the crypt regions of the colon. The intensity of cellular staining in the lamina propria decreased from the small intestine to colon. No immunoreactivity was detectable in the goblet cells. These results indicate that the localization of IGF-I receptors on crypts and villus epithelium in the small intestine suggests a functional role of the receptors in cell growth and differentiation. The localization of the IGF-I receptors in the absorptive cells of the colon suggests that the receptors may mediate short-term metabolic response rather than mitogenic signaling in these differentiated non-dividing cells.