The concentrations of 238U and 232Th have been determined in drinking water samples collected from the Sikar district of Rajasthan State, India. The samples have been analysed by using high-resolution inductively coupled plasma mass spectrometry. 238U content in water samples ranged from 8.20 to 202.63 µg l−1 and 232Th content ranged from 0.57 to 1.46 µg l−1. The measured 238U content in 25 % of the analysed samples exceeded the World Health Organization (WHO) and United States Environmental Protection Agency drinking water guidelines of 30 µg l−1 and 12.5 % of the samples exceeded the 60 µg l−1 Indian maximum acceptable concentration recommended by the Atomic Energy Regulatory Board, India. The annual effective doses (µSv y−1) due to ingestion of 238U and 232Th for different age groups were also calculated. The results compared with the recommended value reported by the WHO.