Introduction: We propose our surgical experience and the decisional algorithm we use to select the surgical procedure for the ulnar nerve entrapment at the elbow according to defined parameters., Materials and Methods: Between 2005 and 2007, 44 patients were operated according to our algorithm that is based both on clinical parameters, classified through the McGowan scale, and on biological ones (the nervous morphology and the amount of scar around the medial epicondyle). Patients were treated through "modified" in situ simple decompression, subcutaneous and sub muscular transpositions., Results: After an average follow-up of 13.4 months, function improved by one grade in 70% of patients, two grades in 16% and there was no change in 14%. Moreover 84.8% of patients operated through the modified in situ decompression technique reported an excellent outcome., Conclusion: We suggest an algorithm for uniformly treat the patients with cubital tunnel syndrome through a clinical and biological point of view. The modified in situ decompression is a safe and effective treatment for the majority of these patients reducing the risk of redo surgery.