Background: Allergic contact dermatitis is a significant cause of both occupational and non-occupational skin disease. Patch testing is an important diagnostic tool for the determination of responsible allergens. Objective: This study reports the results of patch testing by the North American Contact Dermatitis Group from January 1, 2003, to December 31, 2004. Methods: At 13 centers in North America, patients were tested with the same screening series of 65 allergens, with a standardized patch-testing technique. Data were recorded on standardized forms and manually verified and entered. Descriptive frequencies were calculated, and trends were analyzed with chi-square statistics. Results: A total of 5,148 patients were tested. Of these, 3,432 (66.7%) had at least one positive reaction, 2,284 (44.4%) were ultimately determined to have primary allergic contact dermatitis, and 676 (13.1%) had occupation-related skin disease. There were 9,762 positive allergic reactions. Compared to the previous reporting period (2001-2002), allergies to nickel, budesonide, mercaptobenzothiazole, and paraben mix were at least 1.12 times more common (all p values < .03). Compared with the previous 8 years (1994-2002), only the prevalence rates of allergies to nickel and budesonide were statistically significantly higher (p values < .003). Conclusion: Allergic contact dermatitis from nickel and budesonide may be increasing in North America. These results again underscore the value of patch-testing with many allergens.