Structural analysis of the cDNA for the human fibroblast growth factor receptor (flg) revealed the existence of a larger and a shorter isoform of the receptor. The larger form has three extracellular immunoglobulin-like domains. On the other hand, the shorter form deletes the first (the most external) immunoglobulin-like domain region. Two consecutive amino acids (Arg Met) between the first and second immunoglobulin-like domains are sometimes deleted from the shorter form. In this paper, we isolated and analyzed the gene for the human fibroblast growth factor receptor. Organization of the gene revealed that the isoforms are produced by two different types of alternative splicing (the cassette and internal donor types) from the common gene. In human placenta, the shorter form is expressed as the major isoform.