50 children with urinary-tract infection and vesicoureteric reflux were investigated by direct radionuclide cystography (R.N.C.). Recent micturating cystourethrograms (M.C.U.) were used as controls. In 37 patients the results of both tests corresponded, 9 patients were M.C.U. positive only, and 4 were R.N.C. positive only. R.N.C. is associated with a considerably lower radiation dose than M.C.U.S and intravenous urograms, it provides an accurate measurement of residual urine, and is simple to apply with equipment which is readily available. R.N.C. is a useful investigation in the diagnosis and management of reflux and a valuable complement to standard radiographic methods.