The authors have designed and constructed a specific time resolved resonance Raman spectrometer for the study of transient species occurring in photochromic reactions. A homemade, low cost integrating video digitiser associated with the SEC camera head of a modified Coderg UF-76 spectrometer and linked to a PDP-11 minicomputer via a serial interface allows the acquisition and analysis of low light level spectra. This apparatus made it possible to investigate directly the structure of transient photoproducts from pyrrolidinospiropyran.