OBJECTIVE The object of this study was to compare the outcomes of primary and revision transsphenoidal resection (TSR) of nonfunctioning pituitary macroadenomas (NFPMAs) using endoscopic methods. METHODS The authors retrospectively reviewed the records of 287 consecutive patients who had undergone endoscopic endonasal TSR for NFPMAs at their institution in the period from 2005 to 2011. Fifty patients who had undergone revision TSR were retrospectively matched for age, sex, and duration of follow-up to 46 patients who had undergone primary TSR. Medical and surgical complications were documented, and Kaplan-Meier analysis was performed to assess rates of radiological progression-free survival (PFS). RESULTS The median follow-up periods were 45 and 46 months for the primary and revision TSR groups, respectively. There were no significant differences between the primary and revision groups in rates of new neurological deficit (0 in each), vascular injury (2% vs 0), postoperative CSF leak (6% vs 2%), transient diabetes insipidus (DI; 15% vs 12%), chronic DI (2% vs 2%), chronic sinusitis (4% vs 6%), meningitis (2% vs 2%), epistaxis (7% vs 0), or suprasellar hematoma formation (0 vs 2%). However, patients who underwent primary TSR had significantly higher rates of syndrome of inappropriate antidiuretic hormone (SIADH; 17% vs 4%, p = 0.04). Patients who underwent primary operations also had significantly higher rates of gross-total resection (GTR; 63% vs 28%, p < 0.01) and significantly lower rates of adjuvant radiotherapy (13% vs 42%, p < 0.01). Radiological PFS rates were similar at 2 years (98% vs 96%) and 5 years (87% vs 80%, p = 0.668, log-rank test). CONCLUSIONS Patients who underwent primary TSR of NFPMAs experienced higher rates of SIADH than those who underwent revision TSR. Patients who underwent revision TSR were less likely to have GTR of their tumor, although they still had a PFS rate similar to that in patients who underwent primary TSR. This finding may be attributable to an increased rate of adjuvant radiation treatment to subtotally resected tumors in the revision TSR group.