Initial sections of skin biopsies may not be diagnostic of basal cell carcinoma (BCC). Are there histologic predictors of BCC that should prompt deeper sections? Ninety-four cases in which the clinical diagnosis was BCC or "rule-out BCC," and the initial histologic slides were nondiagnostic, were submitted for deeper sections on three additional slides. Of the 94 cases, 50 (53%) demonstrated BCC on deeper sections. This relatively high incidence suggests that deeper sections should be taken in all cases of clinically suspected BCCs unless alternate histologic findings adequately account for the clinical lesion. The results of this study suggest that additional sections are more likely to yield BCC when the initial nondiagnostic slide demonstrates focal epidermal atypia, equivocal adnexae, stromal fibrosis, empty dermal space, and microcalcifications, criteria which may be useful in determining the need to do deeper sections in cases in which BCC is not clinically suspected.