This paper describes the result of some experimental trawl fishing undertaken on a series of cruises in Manila Bay, Luzon, Philippines in 1970. Two commercial medium-sized trawlers were employed using four kinds of trawl nets, namely, two German trawl nets A and B, a Norwegian star net, and a locally made Norwegian net. The fishing observations and the statistical data gathered were concentrated on the catching ability (catch-per-unit-of-effort) of the nets and on the catch composition of each haul. The efficiencies of the four types of nets were shown by the fact that for all nets, more than 50% of the catch was composed of pelagic fish, mostly chub mackerels, anchovies, and hairtails. The German trawl net A proved the most efficient. It was noted, however, that from 1957 through 1962, the catches of the trawlers were made up mostly of two demersal fish species, the sap-sap (Leiognathus sp.) and kalaso (Saurida sp.). There was a considerable decrease in the landings of these two species during the period under review and this was a clear indication of the change toward pelagic fish noted in the catch composition of the trawlers in Manila Bay. A reduction in the catch per unit of effort (catch rate per hour) was observed up to 1966. In 1970, the increase in the catch rate per hour could be explained by the development of better nets (German trawl nets) and the use of more powerful engines.