He isotopic composition was measured for 72 deep-sea sediments from 16 sites in the Pacific and Atlantic oceans and the Japan Sea. 3He content ranges from less than 10-12 cm3 STP/g to about 6¿10-11 cm3 STP/g and 3He/4He from about 10-8 to 1.67¿10-4. The He isotope data lie fairly well on a mixing curve in a 3He/4He-3He diagram, where the end-members of the mixing curve are extraterrestrial He in interplanetary dust particles (IDP's) and terrestrial He in ocean sediments. This confirms the view that there are significant amounts of extraterrestrial He in ocean sediments from global fallout of IDP's into deep-sea sediments. 3He flux estimated for two long cores give a value of about (1.5¿1.0)¿10-15 cm3 STP/cm2 yr over a time span of 40 m.y., which corresponds to an annual fallout rate of IDP's (size<10 μm) of about 400 t. In one of the cores, we observe a ''3He-spike'' which is associated with anomalously high Ir content (1.86¿0.56 ppb). This may be due to meteorite debris. ¿ American Geophysical Union 1987