Background: Fungi may colonize the small intestine and may be pathogenic and/or cause GI symptoms. In one study, 27% of patients with unexplained GI symptoms had SIFO (Jacobs et al). Whether SIFO causes symptoms and whether symptom profiles differ between those with or without SIFO is unknown. Our aim was to determine the presence of fungal overgrowth in patients with unexplained GI symptoms and to compare the symptom profiles of SIFO +ve and -ve patients. Methods: Patients with chronic gastrointestinal (GI) symptoms and negative endoscopy and computerized abdominal tomography (CAT) scan referred to motility center, underwent duodenal aspiration/culture. Under aseptic precautions, 3mL of duodenal juice was aspirated from the 3rd/4th parts of duodenum during esophagogastroduodenoscopy by using a 2mm Liguory catheter and cultured for fungi. Patients scored the frequency, intensity and duration of abdominal pain, belching, bloating, fullness, indigestion, nausea, diarrhea, vomiting, gas for previous 2 weeks on a Likert-like scale from 0-3 (frequency: 0=none, 1= 1 episode/wk. intensity: 0 = no symptoms, 1 = mild, 2 = moderate, 3 = severe symptom. Duration: 0 = none, 1= 30 min.). Mann-Whitney U test was used to compare symptom scores of SIFO +ve vs SIFO -ve patients. Results: 150 patients (F/M=117/33), mean age 47 years, and symptom duration of >6 months were enrolled. Duodenal culture yielded a positive fungal culture in 25.3% (38/150) patients. 37 (97.4%) were Candida spp.; 31 (83.8%) Candida Albicans, 6 (16.2%) Candida Glabrata, and 1 (2.6%) was Penicillum spp. 16 (42.1%) grew ≥102 CFU/ mL, 11 (28.9%) grew ≥103 CFU/mL, 4 (10.5%) grew ≥104 CFU/mL, and 3 (7.9%) grew ≥105 CFU/mL. Predominant symptoms were abdominal pain, bloating, fullness, nausea and gas, but symptom scores were not different between patients with or without SIFO, all p= ns (Table 1). Median total symptom scores were not significantly different in SIFO +ve vs SIFO -ve group; 45.043 vs 46.428 (p=0.651). Conclusion: Approximately 25% of patients with chronic GI symptoms may have SIFO. Symptoms do not appear to differentiate between those with or without SIFO and duodenal culture appears to be the only method of identifying this problem. Table 1