Feeding, respiration, and excretion rates (ammonium and phosphate) of mesozooplankton from the equatorial Pacific upper water column (0–100 m) were measured along the 180th meridian at different stations between 8°S and 8°N, and more repeatedly, at two time series stations, located at 3°S (TSS1) and the equator (TSS2). Only particles of size >8 μm were grazed by the organisms used for the experiments. Grazing rates were higher at TSS1. Ammonium excretion was also maximum at TSS2, resulting in lower O/N values. This suggests that food particles were richer in terms of protein content at the equator, as is also indicated by the lower C/N ratio of particles and the higher proportion of heterotrophic protozoans. Some variations in mesozooplankton specific composition (more carnivorous copepods being present in the equatorial samples) could also explain these O/N differences. Diel variations were observed. Significantly higher grazing, respiration (only at TSS1), and excretion rates were recorded during the day, suggesting that feeding activity was related to the daytime increase of primary production. Using the grazing rates determined under experimental conditions, the grazing pressure on the stock of food particles >8 μm was very low (<1%) and the daily food intake (2.7–3.1% of the zooplankton body carbon), was far from compensating for respiration losses (22% of the body carbon). We conclude that the experimentally measured feeding activity was underestimated because of methodological problems. More realistic values were obtained from energy balance considerations, using measured respiration rates as an indication of minimal carbon requirement and extrapolating to ingestion using literature coefficients for assimilation efficiency (0.7) and net growth efficiency (0.4). According to these calculations the daily food carbon intake necessary to sustain both secondary production and respiration needs would be equivalent to 63% of the mesozooplankton body carbon, and the grazing pressure on >8-μm food particles would reach 14% of the standing stock d⁻¹.