Enterotoxigenic Eschoerchia coli (ETEC) F4 is a major cause of diarrhea in neonatal and young pigs. The locus encoding intestinal receptor for ETEC F4ab/ac has been mapped to pig chromosome (SSC) 13q41. We previously assigned mucin 20 (MUC20) to SSC13q41 and considered it a candidate for the ETEC F4ab/ac receptor. In this study, the full-length mRNA sequence of the porcine MUC20 gene was determined, revealing two MUC20 alternative transcripts differing in an 18-bp deletion in the open reading frame (ORF). The longer isoform is 1,927-bp long and contains a 1,572-bp ORF encoding a protein of 523 amino acids. RT-PCR analysis showed that MUC20 mRNA was expressed most highly in the kidney, prostate, epididymis and bladder. Seven single nucleotide polymorphisms in MUC20 were identified in founder animals of a White Duroc × Erhualian cross, and the entire cross population (n = 842) was genotyped for two MUC20 polymorphisms: g.191C>T in intron 5 and c.1600C>T in exon 6. The transmission disequilibrium test (TDT) results revealed that both polymorphisms were significantly associated with in vitro ETEC F4ab/ac adhesion phenotypes in the intercross population, and the most significant association was found between g.191C>T and F4ac adhesion phenotype (P = 1.02 × 10(-9)).