Background: Sensitivity to mold has been associated with asthma incidence, persistence, and severity. Objective: To examine the relationship between skin test reactivity (STR) to molds and specifically to Alternaria and asthma severity in a group of ethnically diverse children in Connecticut. Methods: Demographics and STR to 14 local allergens, including Alternaria, Penicillium, and mold mix, were obtained for 914 Puerto Rican, African American, and non-Hispanic white children. Results: A total of 126 children (14%) had a positive skin test result to mold, and 58 (6%) demonstrated STR to Alternaria. Compared with non-Hispanic white children, there was no difference in the likelihood of being sensitized to Alternaria for Puerto Rican and African American children (odds ratio [OR] 0.7; 95% confidence interval [CI], 0.3-1.5; and OR, 0.9; 95% CI, 0.4-2.2; respectively). In an adjusted analysis, Alternaria STR was associated with severe, persistent asthma (OR, 3.4; 95% CI, 1.2-8.6) but did not predict increasing asthma severity. STR to cat (OR, 2.5; 95% CI, 1.3-4.9) and dog (OR, 2.9; 95% CI, 1.3-6.0) was also associated with severe persistent asthma. Alternaria STR was associated with severe persistent asthma independent of the total number of positive skin test results. Conclusions: Mold and Alternario STR were uncommon among children in Connecticut. Alternaria STR was not associated with increasing asthma severity but was associated with severe, persistent asthma independent of the total number of positive skin test results. There was no association between ethnicity and Alternaria STR. Ann Allergy Asthma Immunol 2011;106:301-307.