The relationship between serum and saliva paracetamol concentrations was investigated in twenty healthy volunteers. The plasma and saliva drug concentrations showed a significant correlation (r = 0.67). However the agreement between the two methods of measurement was poor with limits of agreement of -15.3 mg l-1 to +15.9 mg l-1 with mean sample values of 19.2 and 19.5 mg l-1 for plasma and saliva, respectively.