Soybean crinkle leaf, a new whitefly-borne disease affected soybean in Thailand. Infected soybean plants showed twisting or curling of leaves with veinal enations on the undersurface of the leaves. The disease agent was transmitted by the whitefly, Bemisia tabaci Genn. in a persistent manner and by grafting, but not by aphids, inoculation of sap or through seeds of soybean. Single whiteflies did not transmit the disease agent and about 40 insects were necessary for achieving high transmission rates. Minimum acquisition and inoculation access periods ranged between 30 and 60 min and about 10 and 30 min, respectively. Latent period in the whitefly vector ranged between 8 and 10 hr, and retention period in the vector lasted 9 days. The disease affected 11 plant species in three families (Compositae, Leguminosae, and Solanaceae) after whitefly transmission. Purified preparations of the causal agent revealed the presence of a large number of geminate particles, and also aggregations of virus-like particles were observed in the nuclei of infected cells, suggesting that the causal agent of the disease is a possible member of geminivirus.