This paper describes a method for non-radioactive in situ hybridization providing subcellular localization of mRNA in 3 microns cryosections. We used two alternative colorimetric reactions to detect digoxigenin-labeled cRNA probes: alkaline phosphatase and HRP (horseradish peroxidase). With some probes the signal with the alkaline phosphatase reaction was intense, and diffusion of the reaction product was noticeable. Using HRP-conjugated antibodies improved the resolution but decreased the sensitivity of the signal. Photoamplification of the HRP reaction product increased the contrast and improved the sensitivity of the technique.