Resistance to carbaryl, lindane and methidathion was studied in field and laboratory strains of Dysdercus fasciatus Sign., D. nigrofasciatus Stål, D. superstitiosits (F.) and D. cardinalis Gerst. from Kenya. Four-day old fifth-instar female nymphs were found to be the most convenient for bioassay. The LC50s of carbaryl, lindane and methidathion for D. fasciatus were 372, 240, and 110 mg/litre, respectively, those for D. nigrofasciatus 337, 294, and 111 mg/litre, and that for carbaryl for D. cardinalis 147 mg/litre. The Meru and Ngwata strains of D. fasciatus had resistance factors of ×5·3 and ×6·1, respectively, to carbaryl. The field strains of all four species showed slight resistance (up to ×3·4) to lindane and methidathion. The poor control of Dysdercus spp. experienced in Eastern Province, Kenya, is probably due to the development of resistance to carbaryl. A laboratory and a field strain of each of D. fasciatus and D. nigrofasciatus were subjected to carbaryl selection pressure for six generations of doses equivalent to the LC50-LC70. The laboratory strain of D. fasciatus was also subjected to lindane selection for six generations. The laboratory and field strains of D. fasciatus developed resistance to carbaryl of ×3·7 and ×5·7, respectively, and cross-resistance to lindane of up to ×2·7. No significant increase in resistance was observed in D. nigrofasciatus after selection. The laboratory strain of D. fasciatus developed resistance to lindane of ×5·5 after selection and cross-resistance to carbaryl of ×4·3.