A fiber-specific cDNA clone (GCW1) was isolated from a cotton fiber cDNA library using a differential screening method. Nucleotide and derived amino acid sequence analyses indicated that GCW1 encodes a proline-rich cell wall protein. Northern blot analysis showed that the cell wall protein gene is developmentally regulated and is preferentially expressed in fibers. The promoter region of the GCW1 gene was obtained by a long distance PCR amplification method.