1. During the period 24 January - 6 March 1967 the R/V ARGO was engaged in oceanographic research in the Eastern Pacific Ocean as part of the EASTROPAC Project which is an attempt to develop the pelagic tuna resources through a thorough knowledge of the environ- mental features of the region. The ship departed San Diego heading south for 20°N-119°W. Then it sailed south to 20°S-119°W where it turned east to 126°W and then north again to 20°N-126°W. From there it returned to San Diego. The major area of interest was between 20°N and 20°S. In this region environmental data were collected at approximately 20 mile intervals. As part of this program bird and mammal observations were made by me for a total of 42 days. This preliminary report summarizes these observations. A total of 429.08 diurnal hours was spent observing while the ship traveled 3,354 miles. An additional 15.25 hours of observations were made at night while the ship was stopped on stations. During the daylight hours a total of 3,917 birds of 38 species was seen. Fourteen birds of 4 species were seen at night. Sooty Terns (2,313) and Leach's Storm Petrels (749) were the dominant birds in the whole area. Only one other species (Wedge-tailed Shearwater) was seen in numbers greater than 100. Tables 1-11 summarize all the observations made and Figures 1-19 show the distribution of several of the species. Further information is provided in the Species Account section. This report is only a preliminary report and will be modified after the environmental data are analyzed.