A relatively low-cost computer-assisted image analysis system is described. Software has been specifically written for the continuous monitoring of absorbance readings on cryostat sectons of plant tissues incubated in media to reveal enzyme activities. The equipment was tested by quantify ing glucose-6-phosphate dehydrogenase activity in cryostat sections from shoot apices of spinach plants. The reaction rate of the dehydrogenase activity was monitored at two incubation temperatures, 20°C and 30°C. Control incubations were performed in media lacking substrate. The specific test minus control reaction at 30°C was twice that at 20°C. Variation of the substrate concentration at 30°C yielded a Km value of 0.37 mM. These preliminary results show that our image analysis system can be used for kineti measurements of dehydrogenase activity in froizen tssue sections and constitute a new approach for enzyme histochemistry in the shoot apicla meristem.