Aggressive-growth basal cell carcinoma (AG-BCC) defines a group of basal cell cancers that are histologically and clinically aggressive. This group includes morpheaform, infiltrating, and recurrent BCCs. Because of the clinical observation that the incidence of AG-BCC may be increased in patients under 35 years of age, compared with those older, we performed a retrospective study. We reviewed the pathologic findings of 3381 patients diagnosed with BCC, including 102 patients with BCC referred for Mohs surgery to determine whether AG-BCC occurs with increased frequency in patients younger than than 35 years of age. Among patients under 35 years of age, 38% of women had AG-BCC compared with 9% of women in the older age group. Similarly, 25% of men under 35 years of age had AG-BCC compared with 11% among men in the older age group. Aggressive-growth BCC is more frequently noted in patients under 35 years of age than in those older. Failure to diagnose this type of BCC, which may be clinically subtle, may lead to incomplete or inadequate treatment. Because of the tendency of these tumors to recur, greater long-term morbidity may result.