Patients with non-obstructive azoospermia (NOA) with a previous failed conventional TESE (cTESE) may undergo a salvage microdissection testicular sperm extraction (mTESE) with the probability of successful sperm retrieval (SSR) being almost dependent upon the number of previous surgical attempts and to different histopathologic categories OBJECTIVES: To determine whether the seminiferous tubules (STs) pattern and the histological categories could affect the sperm retrieval rate (SRR) in patients with NOA undergoing salvage mTESE after failed cTESE MATERIALS AND METHODS: 79 patients undergoing unilateral of bilateral salvage mTESE were evaluated.