The transparency of the juvenile zebrafish and its genetic advantages make it an attractive model for the study of intestinal differentiation and renewal. Antibody 3G12 marks goblet cells specifically. It labels both the mucus compartment and other parts of the cytoplasm. On Western blots, 3G12 stains diffuse bands, consistent with variably glycosylated antigen(s). 3G12 labelled cells are concentrated in the posterior gut. 3G12 is a marker for mucus secreting cells in the posterior gut of zebrafish.