We have molecularly cloned and sequenced cDNA to the transcript of H-ras-1, the transforming gene of the T24 human bladder carcinoma cell line. The transcript derives from at least five exons in the H-ras-1 gene, and RNA splicing occurs at sites typical of exon-intron junctions. T24 H-ras-1 RNA has an AUG-initiated open reading frame of 567 nucleotides, which can encode a protein of mass comparable to the apparent molecular weight of the T24 H-ras-1 gene product. The T24 H-ras-1 gene product is nearly identical to v-H-ras p21, the transforming protein encoded by the genome of Harvey sarcoma virus. We discuss the implications of this sequence conservation in the structure-function relationships of ras proteins.