Twenty-megahertz ultrasound is a potentially useful noninvasive method for the preoperative determination of tumor dimensions and for defining tumor margins and shape.1 Using 20-MHz ultrasound equipment (Dermascan C; Cortex Technology, Hadsund, Denmark), we examined 35 different types of skin tumors (basal cell carcinoma [n = 12], nevus pigmentosus [n = 9], dysplastic nevus [n = 3], dermatofibroma [n = 3], fibropapilloma [n = 2], seborrheic keratosis [n = 2], malignant melanoma [n = 1], lipofibroma [n = 1], neurofibroma [n = 1], and keratosis actinica [n = 1]) before surgery. The maximal vertical diameter of the tumors was determined by combined A- and B-mode. After ultrasound examination, the tumors were surgically removed and a definite diagnosis was made. Hematoxylin-eosin–stained sections were histopathologically examined to determine the maximal vertical diameter of the tumors using an ocular micrometer. The tumor dimensions were statistically correlated (linear correlation and t test).