Seasonal circulation in the Indonesian Seas is investigated in detail by use of a high-resolution oceanic general circulation model forced by the monthly mean climatological wind stress. Although the net barotropic through flow between the Pacific and Indian oceans is not permitted, the model appears to be successful in predicting the observed transport through the Lombok Strait. The modeled transport varies from almost nothing in January to 5 Sv in September, with a local minimum in June; this seasonal variation is regulated by means of remote action of the monsoonal winds in the tropical Indian Ocean as well as local and remote action of the monsoonal winds over the western Pacific. The drainage into the South China Sea through the Java Sea during the boreal summer may explain the apparent local minimum of the modeled Lombok through flow. The root cause of the semiannual aspect of the Lombok through flow, however, lies in the Wyrtki jets of the Indian Ocean, which reduce the positive pressure gradient across the Lombok Strait twice a year. ¿ American Geophysical Union 1993