There are two antigenic types of human virus-induced interferons (IFNs): one is a human leukocyte IFN (Hu IFN-alpha and the other is a human fibroblast IFN (Hu IFN-beta). We examined the antigenic types of IFNs produced in several human T and B lymphoblastoid cell lines through the induction by Sendai virus. We could produce IFNs in the several human T lymphoblastoid cells (RPMI 8402, Peer, JM and CCRF-CEM) and in several human B lymphoblastoid cells (BALL-1, B35M, DG-75 and ARH-77), and examined antigenic types of the IFNs produced. The results showed that all T lymphoblastoid cells produced Hu IFN-beta. On the other hand, the antigenic types of IFN were dependent on each cell line in human B lymphoblastoid cell lines. The IFN produced in BALL-1 cell was only one type of Hu IFN-alpha. The IFNs produced in ARH-77 and DG-75 cells contained two types of the Hu IFN-alpha and Hu IFN-beta. The IFN produced in B35M cell was only one type of Hu IFN-beta. It was concluded that human T lymphoblastoid cell produced Hu IFN-beta, and that the first type of human B lymphoblastoid cell produced only Hu IFN-alpha, the second type produced Hu IFN-alpha and Hu IFN-beta and the third type produced only Hu IFN-beta.