Goswami,-S.C.; Goswami,-U. Diel variation in zooplankton in Minicoy Lagoon and Kavaratti Atoll (Lakshadweep Islands). INDIAN-J.-MAR.-SCI. 1990. vol. 19, no. 2, pp. 120-124. Diel variations in occurrence and abundance of zooplankton in the Minicoy lagoon and surrounding sea outside the coral reef at Kavaratti Atoll, Lakshadweep, were studied. Zooplankton standing stock (biomass) values showed wide variations in the lagoon compared to surrounding sea. Meroplankton constituted an important component of zooplankton community in the lagoon and nocturnal abundance was more pronounced. Copepods dominated the holoplanktonic forms. Copepod species diversity and equitability indices gave an inverse relationship with zooplankton biomass in the surrounding sea samples while direct relationship was obtained in the lagoon samples. Higher incidence of carnivorous pontellid copepods in the night collections was a characteristic feature which was not observed from lagoons elsewhere including the Lakshadweep archipelago.