A randomized crossover trial on the effect of salt restriction on blood pressure was carried out involving 124 adolescents (mean age 16 years). Dietary sodium was reduced from approximately 110 to 45 mEq/24 h for a period of 24 days. Blood pressure was non-significantly lower at the end of the experimental diet for all participants. A slight (0.7 kg), yet statistically significant fall in weight was observed (P less than 0.05). Subgroup analysis demonstrated that participants whose body mass index was below the median had a statistically significant fall in systolic blood pressure (P less than 0.05); fall in weight and increase in heart rate were also more pronounced in the less obese individuals. It would appear that moderate sodium reduction does not have an overall short-term effect on blood pressure in normotensive adolescents. However, body size as reflected in body mass index may influence blood pressure response to sodium reduction.