Twelve upper Pliocene--lower Pleistocene nannofossil events are calibrated with oxygen isotope stratigraphy at eight DSDP/ODP sites ranging from 53¿N to 41¿S latitudes in different oceans in order to determine their ages and to reveal their synchrony or diachrony within a significantly higher-resolution time scale than the geomagnetic polarity time scale allows. Six nannofossil vents appear to be synchronous from low to middle latitudes (the last occurrences of Reticulofenestra asanoi (oxygen isotope stage 22), Gephyrocapsa spp. A-B (stage 37), Discoaster brouweri (stage 71), Discoaster surculus (stage 99), Discoaster tamalis (stage 111), and the first occurrence of Gephyrocapsa spp. A-B (stage 59)), five appear to be diachronous (the first occurrences of Gephyrocapsa spp. C-D, Reticulofenestra asanoi, and Gephyrocapsa spp. A-B larger than 5.5 μm, and the last occurrences of Helicosphaera sellii and Discoaster pentaradiatus), and one is synchronous at low latitudes (the last occurrence of Calcidiscus macintyrei). ¿ American Geophysical Union 1993