Population growth of the rice planthoppers, Nilaparvata lugens and Sogatella furcifera, in direct-seeded fields of the Muda area, West Malaysia was generally characterized by (1) a low immigrant density in the early rice stage, (2) two complete consecutive generations and a 3rd optional generation, (3) high population growth rates up to the 2nd generation, and (4) low population growth rate from the 2nd to the 3rd generations. However various population growth patterns were also observed in both planthopper species. In addition, no relationship was found between the immigrant density in the early rice stage and subsequent population size in the late rice stage. Most cases of hopperburn in the 1st cropping season of 1990 occurred in early-planted fields seeded soon after the crop-free fallow period implemented during the dry season, Field surveys also showed that both planthoppers reached high densities in an early-planted field, in spite of the very small number of immigrants, whereas the densities of planthoppers in a late-planted field exhibited a very low level, in spite of the large number of immigrants in the early rice stage. The paucity of natural enemies seemed to promote the rapid increase of the number of planthoppers in the early-planted field. Since natural enemies were numerically dominant and the survivorship of the young planthopper nymphs was relatively low in the late-planted field, it was assumed that natural enemies contributed to the suppression of the planthopper population in this field. On the basis of these results, it was concluded that the interaction between planthoppers and their natural enemies was a major factor determining the population growth patterns of planthoppers in the Muda area. The dry season, particularly with the implementation of crop-free fallow period presumably enabled to eradicate both planthopper species and their natural enemies. This environment seemed to provide favorable conditions for population growth of planthoppers in the earlyplanted fields in the 1st cropping season. Continuous planting appeared to promote natural enemy activity provided that the biotic community in the fields was not disturbed.