Abstract: The results of an interlaboratories round-robin comparison of hydrophone calibration techniques in the frequency range 0,1 Hz - 200 kHz carried out in Russia in 1993-97 are described. Six hydrophones of two types were circulated to twelve laboratories involved in defence, education, shipbuilding, and state metrology activity. Both types of hydrophones were designed in All-Russian Scientific Research Institute for Physical-Technical and Radiotechnical measurements (VNIIFTRI). Each laboratory determined the open-circuit end-of-cable hydrophone sensitivity using their normal calibration methods. The agreement between all the participants was within 1 dB at frequencies 0,1 Hz -100 kHz and within 2 dB at frequencies 100 - 200 kHz.