The possibility of differentiating between sedative‐hypnotics and centrally acting muscle relaxants has been investigated in mice. The ED50 values for loss of muscle tone and loss of righting reflex were determined for 2‐(3î,6î‐dioxaheptyl) aminomethyl‐1,4‐benzodioxane (ambenoxan), 2‐(4î,7î‐dioxaoctyl) aminomethyl‐1,4‐benzodioxane (WB 4123) and compared with mephenesin, meprobamate, methocarbamol and the sedative‐hypnotic, sodium pentobarbitone. Comparison of the slopes of the regression lines for hypotonia and loss of the righting reflex for the compounds suggests that ambenoxan offers a greater separation between the two responses than clinicall