This is the final report of a Russian-Chinese international comparison of hydrophone calibration methods conducted by exchanging hydrophones between the Hangzhou Applied Acoustics Research Institute (HAARI) and the All-Russian Scientific and Research Institute for Physical-technical and Radio-technical Measurements (VNIIFTRI). The comparison was organized in 1997/98 in order to assess the current state of the art for hydrophone calibration in the Russian Federation and China. Six hydrophones of different types were calibrated using the Russian and Chinese Underwater Pressure National Standards in the frequency range 1 Hz to 630 kHz. The following methods and facilities for hydrophone calibration were used during the comparison: piezoelectric compensation in a closed chamber, vibrating column in an open chamber, and free-field reciprocity in the laboratory tanks. Some features and nuances of these facilities are considered. The agreement of 140 calibration data was checked for six hydrophones. The mean and maximum differences between the participants' results were 0.24 dB and 1.6 dB, respectively.