Esophageal manometry (EM) and ambulatory pH monitoring (APM) have been used in preoperative physiological evaluation of patients with refractory GERD who are being considered for laparoscopic antireflux surgery. Spastic disorders on EM, particularly nonspecific spastic disorders, and absence of GERD on APM each predict more postoperative symptoms and poorer surgical outcome. 1092 patients (613 female and 469 male) referred for pre-operative EM (720 for both EM and APM) were examined to determine the rates of these poor outcome predictors and their gender distribution within the patient population. Methods: High-resolution EM was performed on each subject using a 21-lumen water-perfused system and categorical pattern classification scheme with 4 principal categories: normal, hypomotility (body and/or lower esophageal sphincter), hypermotility [achalasia, spastic disorders (diffuse esophageal spasm, nonspecific spastic disorders)], and mixed disorders. APM was performed for at least 20 hours with either standard catheter or wireless systems. GERD was evident from APM if thresholds for acid exposure time and/or positive symptom association probability (SAP) were passed. Results: Hypomotility was found in 188 (36.7%) females vs 205 (43.7%) males, while hypermotility was found in 192 (31.3%) females vs 93 (19.8%) males (p<0.001 for each comparison). Within the latter group, 172 (28.1%) females had nonspecific spastic disorders vs 68 (14.5%) males (p<0.001); other hypermotility disorders were equally distributed. Distribution of EM patterns was nearly identical to the entire group in the subset of 720 patients who also underwent APM (p=0.5). Among these patients, 115 (27.0%) females and 55 (18.7%) males showed no objective evidence of GERD (p=0.01). Of the 550 subjects with abnormal APM, 43 (7.8%) demonstrated only positive SAP with normal acid exposure time, including 36 (11.6%) females and 7 (2.9%) males (p<0.001). Overall, 197 (46.2%) females presented with at least one poor outcome predictor compared with 102 (34.7%) males (p=0.002). Conclusions: Female patients being considered for laparoscopic antireflux surgery are at greater risk of having EM and APM findings associated with persistent symptoms and poorer surgical outcome, although these findings are present in many patients of either sex at preoperative evaluation. Both nonspecific spastic disorders and absence of GERD indicators on APM are more common in females. The explanation may rest in part on greater esophageal sensitivity to physiological events in this sex.