A new 11-layer hemodialyzer (AB Gambro) was tested in vitro at a low dialysate flow of 500 ml/min and a high dialysate flow of 4 liters/min with recirculation and compared in performance at the low dialysate flow to a two-layer Kiil dialyzer. Metabolite removal was superior to that of the conventional Kiil dialyzer. Shorter dialysis times (six hours) appear to be possible with the new dialyzer. It has a relatively low priming volume. The design is unique, allowing it to be mass-produced and massassembled. The new dialyzer offers a definite hygienic advantage by being presterilized and totally disposable.