To obtain prolactin (PRL) cell ablation in trout, we were interested in producing transgenic fish in which a cytoplasmic toxin gene would be driven by a PRL enhancer/promoter. Recently, Chinook salmon PRL gene was isolated and fully sequenced by Xiong et al.1 The 2.4 kb of the 5′ flanking sequence has been demonstrated to drive expression of a reporter gene in vitro in a cell-specific manner. 2 Moreover, when co-transfected with transcriptionnal factor Pit 1 specific to PRL cells, this promoter led to CAT expression even in nonpituitary cells. This study analyzes the cell-specific expression of a reporter gene driven by cis regulatory elements of the salmon PRL gene (2.4 kb of the 5′ flanking sequence) in stable lines of transgenic rainbow trout (Oncorhynchus mykiss). Thus, this work focuses on integration, transmission, and cell-specific expression of this construct.