Objectives: Small intestinal bacterial overgrowth (SIBO) is often present in patients with chronic pancreatitis (CP) with persistent steatorrhea, despite pancreatic enzyme replacement therapy (PERT). Overall prevalence of SIBO, diagnosed by glucose breath test (GBT), varies between 0-40% but 0-21% in those without upper gastrointestinal (GI) surgery. We investigated the prevalence and non-surgical independent predictors of SIBO in CP without upper GI surgery.Methods: 273 patients ≥18 years-old had a presumptive diagnosis of CP and a GBT between 1989-2017. We defined CP by Mayo Score (0-16) ≥4 and a positive GBT for SIBO by Rome Consensus Criteria, and retrospectively collected data for 5 a priori variables (age, opiates, alcohol use, diabetes mellitus (DM), gastroparesis) and 41 investigational variables (demographics, GI symptoms, comorbidities, CP etiologies and co-factors, CP symptom duration, Mayo score and non-diabetes components, and biochemical variables).Results: 98 of 273 patients had definite CP and 40.8% had SIBO. Five of 46 variables predicted SIBO: opiates, p=0.005; DM, p=0.04; total Mayo score, p<0.05, zinc, p=0.005, and albumin, p<0.05). Multivariable analysis of 3 non-correlated variables identified zinc level (OR=0.0001; p=0.03) as the sole independent predictor of SIBO (model C-statistic=0.89; p<0.001).Conclusions: SIBO, diagnosed by GBT, occurs in 40.8% of patients with CP without upper GI surgery. In CP patients, markers of more severe CP (low zinc level, DM and increased Mayo