A cumulative data set from the eastern North Atlantic was compiled and analysed to study the population dynamics of Globigerina bulloides. Data were generated from samples collected with a multiple opening and closing plankton net from the upper ocean (0-500 m). We analysed the total assemblage > 125 μm. The habitat of G. bulloides in the eastern North Atlantic is restricted mostly to the upper 60 m of the water column and depends on the availability of its food resources and, therefore, on the general hydrographic pattern. The temporal distribution of tests at different depths reveals a systematic succession that is related to the lunar cycle. We suggest that G. bulloides reproduces mainly within the upper 60 m of the ocean. Gametogenesis is unusual in test size classes below 125 μm but frequent in specimens larger than 150 μm. Reproduction takes place during the first week after new moon. Maturation of specimens takes place during the second half of waxing moon and during waning moon. Large numbers of mature specimens [gametogenic calcification (GAM) specimens > 250 μm] occur during the time of main reproduction.