We have compared the high-performance liquid chromatographic method with the direct barbituric acid test in an assessment of nicotine exposure. The effect of the endogenous colour in urine on the direct barbituric acid method was also studied. The applicability of methods was evaluated with urine samples from 15 smokers who smoked 5, 10 and 20 low- and medium-nicotine cigarettes per day. Assessments of nicotine intake with the methods were well correlated, although the high-performance liquid chromatographic method detects only cotinine and the direct barbituric method most of the nicotine metabolites. Before endogenous colour subtraction in the DBA method the correlation coefficient was 0.558 and after that 0.784. Both methods indicated similar changes in nicotine exposure with the change of brand and also a dose dependent relationship to the number of cigarettes smoked. The coefficients of variation for both of the methods were 3.4%. The endogenous colour determination lessened the capacity of direct barbituric acid method to one half being about 150 samples per day. With the high-performance liquid chromatographic method the capacity was about 50 samples per working day.