Epidemiological studies investigating the risks associated with shoulder impingement are non-existent. Baseline data of prevalence are reported from a large cohort of workers (n=860) in 12 diverse plants in Wisconsin and Utah. The workers are 67.3% female, 28.4% current smokers, 22.7% former smokers, with a mean age of 41.4+/-11.2 years and mean Body Mass Index (BMI) of 29.5+/-6.9 kg/m2. All workers underwent a questionnaire, structured interview, and two standardized physical examinations. Findings herein are for the right shoulder only. At baseline, a total of 25.9% had complaints of glenohumeral pain in the prior month and 11.4% had a positive impingement (Neer's) sign. Using the impingement case criteria of glenohumeral pain and a positive impingement sign, the one month period prevalence of right shoulder impingement in this population is 8.7%. Univariate and multiple logistic regression analyses were performed. Univariate analyses yielded statistically significant associations with age [Odds Ratio (OR)=1.04, 95% Confidence Interval (CI) 1.02, 1.07], diabetes mellitus (OR=3.00, 95% CI 1.27, 7.07) and job dissatisfaction (OR 3.73, 95% CI 1.39,10.07). After adjustment for age, BMI, gender, smoking status, diabetes mellitus, a question on familial psychosocial problems, and job dissatisfaction these data demonstrated similarly robust findings. Age (OR=1.05, 95% CI 1.02, 1.08], diabetes mellitus (OR=2.63, 95%1 CI 1.03, 6.72) and job dissatisfaction (OR=4.47, 95% CI 1.59, 12.57) were statistically significant. The findings concerning age are comparable with other published necropsy studies on shoulder tendinitis, however the relationship with diabetes mellitus is new. The relationship with job satisfaction is similar to one prior report on shoulder pain. These results suggest that there are personal factors that are strongly associated with shoulder impingement after adjustment for known and suspected risk factors.