Background Since 2005 when we became aware of pectoralis minor syndrome (PMS), more than 75% of patients diagnosed with neurogenic thoracic outlet syndrome (NTOS) also have neurogenic PMS (NPMS), and about 30% have only NPMS, without NTOS. Methods Diagnosis was made based on history, physical examination, pectoralis minor (PM), and scalene muscle blocks with lidocaine. Pectoralis minor tenotomy was performed as an outpatient procedure under local anesthesia with heavy sedation through a 5-7 cm transaxillary incision. Results The clinical picture included pain or tenderness in the anterior chest wall and axilla, together with physical findings of tenderness over the pectoralis minor tendon. Other symptoms were extremity pain, weakness, and paresthesia, similar to symptoms of NTOS. In 76 patients, 100 operations were performed: 48 for NPMS combined with NTOS and 52 for NPMS-alone. Features distinguishing the PM-alone group were fewer and milder occipital headaches, less neck pain, and fewer positive physical findings. Preoperatively, 85% of the of the PM-alone group were still employed compared to only 57% of the combined group (p=0.01). Success rates with 1-3-year follow-up for the PM-alone group were 90% good-excellent, 2% fair, and 8% failed; for the combined group success rates were 35% good-excellent, 19% fair, and 46% failed. All but one of the failures was immediate, only one was late. The only complication was 3 wound infections. Most patients returned to work within a few days. In the combined PMS/TOS group, most of the failed patients subsequently had thoracic outlet operations. Conclusion PMS commonly accompanies NTOS and frequently exists alone. Its recognition is important as many patients with suspected NTOS can be treated successfully with a simple, essentially risk-free PM tenotomy. Should this fail, thoracic outlet decompression can always be performed at a later date.