The effect of ethanol on rats was investigated at increasing rates of acceleration for bar rotation speed. Ethanol was given to rats by a liquid diet starting with 2.4% ethanol (v/v) for 3 days. Then the ethanol concentration was increased to 4.8% (v/v) for 3 days and finally to 7.2% (v/v) for 15 days. Accelerod performance was recorded before and throughout 20 days of ethanol intake. Mean blood ethanol levels were 266.34+/-13.11 and 285.20+/-9.77 mg/dl on the 7th and 15th days of ethanol (7.2% v/v) consumption, respectively, as measured in a parallel group of animals. Ethanol produced significant concentration-dependent impairments in the accelerod performance of rats. The motor impairment effect of ethanol was most prominent in the test using the greatest rate of acceleration (from 0 to 79 rpm within 2 min). The impairment effect of ethanol on accelerod performance occurred throughout the period of ethanol exposure. Our results indicate that motor impairment on the accelerod performance test produced by an ethanol liquid diet depends on the concentration of ethanol and the rate of acceleration. In addition, under free-access conditions accelerod performance may not be a suitable behavioral test for detecting tolerance development to ethanol in rats.