PDE5 inhibitor Tadalafil has been approved for the treatment of BPH symptoms, but where PDE5 is expressed in the prostate remains a mystery.In the literature five studies have reported immunolocalization of PDE5 in the prostate.Uckert et al.concluded that PDE5 is mainly expressed in the glandular structure, but Zenzmaier et al., Fibbi et al., Morelli et al., and Zhang et al.all said that PDE5 is undetectable in the epithelium.Still, while Zenzmaier et al.and Zhang et al.found that PDE5 is mainly expressed in the fibromuscular stroma, Fibbi et al.and Morelli et al.said that PDE5 is undetectable in the fibromuscular stroma and is mainly expressed in the vascular endothelium and smooth muscle.However, it should be noted that the histological images in the latter studies were acquired at 4× or 10× magnifications, which are too low for discerning such structures.