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We have investigated the expression of human interferon (IFN)-related transcripts in Sendai virus-induced lymphoblastoid (Namalwa) cells and in poly(I) X poly(C)-induced fibroblast (FS-4) cells by electrophoresis of RNA through agarose-CH3HgOH gels followed by (a) blot hybridization of the RNA using IFN-alpha 1 and IFN-beta 1 cDNA probes, and (b) translation of the eluted RNA into biologically active IFN using the Xenopus laevis oocyte assay. In Namalwa cells induced with or without prior treatment with bromodeoxyuridine we can detect IFN-alpha 1 hybridizable, translationally active, cytoplasmic RNA of lengths 0.3-0.6, 2-3, 3.5-5, and 7-8 kb in addition to the expected 0.8-1.4-kb RNA and IFN-beta 1-hybridizable, translationally active, cytoplasmic RNA of lengths 0.9 kb and approximately 4 kb. However the translationally active 1.8-kb IFN-alpha L mRNA(s) in Namalwa cells (P. B. Sehgal, May, LaForge, and Inouye, Proc. Nat. Acad. Sci. USA 79, 6932-6936, 1982) appears to have less than 60-70% nucleotide sequence homology with IFN-alpha 1 in the coding region because it does not cross-hybridize IFN-alpha 1 cDNA even under very relaxed hybridization conditions. In induced FS-4 cells we can detect IFN-beta 1-hybridizable and translationally active cellular RNA of lengths 0.3-0.4, 0.65, 0.9, 1.8, 2-3, 3.5-5, and 7-8 kb. No hybridization is detected in RNA of length 1.3 kb ("IFN-beta 2 mRNA"). Direct comparisons between the translation and hybridization data using dot-blot hybridization procedures confirm that the apparently subcistronic 0.35-kb IFN-beta 1 hybridizable-RNA species detected in FS-4 cells is translationally active.