To determine the species composition of the zooplancton in the reservoir Betania (altitude; 560 m.a.s.l.; area: 7.4 km 2 ; vol: 1971 x 10 6 m 3 ; mean depht 28 m), at seven sites and several depths, bimonthly net samples (100 and 200 microns mesh size) were taken during 1991. Alltogether 24 species were found: Thermocyclops decipiens (Crustacea, Copepoda), Moina sp., Ceriodaphnia cornuta y Allona sp. (Crustacea, Cladocera); 19 species of rotifers, of which 7 belong to the genus Brachionus, as well as larvas of the dipter Chaoborus sp. For the first time Brachionus havanaensis, B. falcatus falcatus, b. quadridentatus, y Platyias cuadricornis f. brevispinus were found in Colombia. The species composition was compared with the composition of other lakes and comparison shows that the Betania reservoir has a typical species composition for warms tropical lakes.