Abstract A convenient, column type, flow-through non-equilibrium radioimmunoassay for insulin is described. Total incubation time is about one hour. No centrifugation or mechanical mixing in the column is required. Reproducibility, sensitivity, specificity, recovery, and parallelism are adequate for clinical utility. Insulin levels in a variety of sera assayed by this column method agree well with results from other more conventional radioimmunoassay methods.