Brachytherapy, which refers to short-distance treatment via implanted sources, requires an accurate knowledge of the dose distribution in the implant volume. A critical step in the determination of the dose distribution involves an accurate calibration of brachytherapy source strength. Following the guidelines recommended by AAPM Task Group No. 22, a routine calibration procedure for brachytherapy sources 137-Cs, 192-Ir, and 125-I has been developed. The calibration of sources is performed with a well-type dose calibrator using standard calibrated sources obtained from the American, British, and French national laboratories. Selected characteristics of the dose calibrator are reported, and some of the problems associated with the dose calibrator are discussed. The results of a comparison of the calibrated sources from the three national laboratories are presented.