A flow monitor system is described that permits a column chromatogram to be monitored at two or more wavelengths spectrophotometrically and for radioactivity of two different isotopes. Radioactivity is measured on part of the effluent, which is mixed with a dioxane-based scintillator for passage through a polyethylene coil flow cell in a dual-channel liquid scintillation flow monitor. An efficiency of up to 14% is obtainable for 3H and 70% for 14C. © 1968.