Treacher Collins syndrome (TCS) is caused by mutations in the TCOF1 gene. This gene encodes a serine/alanine-rich protein called treacle. The structure of the entire TCOF1 gene was investigated in a patient with TCS. We detected a novel deletion (376delAAGGTGAGTGGGACTGCC) spanning 3 bp of exon 4 and 15 bp of the adjacent intronic sequence. This mutation causes premature termination of translation, resulting in a truncated protein devoid of nucleolar localization signal, and potential phosphorylation sites. Real-time PCR analysis showed different melting temperatures of the amplified fragment containing normal allele and that harboring the 18 bp deletion, thus providing a rapid screening assay for this and other deletions of the TCOF1 gene.