Skin biopsy is one of the most important diagnostic tests for skin disorders. Punch biopsy is considered the primary technique for obtaining diagnostic full-thickness skin specimens. It requires basic general surgical and suture-tying skills and is easy to learn. The technique involves the use of a circular blade that is rotated down through the epidermis and dermis, and into the subcutaneous fat, yielding a 3- to 4-mm cylindrical core of tissue sample. Stretching the skin perpendicular to the lines of least skin tension before incision results in an elliptical-shaped wound, allowing for easier closure by a single suture. Once the specimen is obtained, caution must be used in handling it to avoid crush artifact. Punch biopsies are useful in the work-up of cutaneous neoplasms, pigmented lesions, inflammatory lesions and chronic skin disorders. Properly administered local anesthesia usually makes this a painless procedure. Skin biopsy is the most important diagnostic test for skin disorders. In selected patients, a properly performed skin biopsy almost always yields useful diagnostic information. Some authors believe that most errors in dermatologic diagnosis occur because of failure to perform a prompt skin biopsy. Punch biopsy is considered the primary technique to obtain diagnostic, full-thickness skin specimens. It is performed using a circular blade or trephine attached to a pencil-like handle. The instrument is rotated down through the epidermis and dermis, and into the subcutaneous fat. The punch biopsy yields a cylindrical core of tissue that must be gently handled (usually with a needle) to prevent crush artifact at the pathologic evaluation. Large punch biopsy sites can be closed with a single suture and generally produce only a minimal scar. Because linear closure is performed on the circular-shaped defect, stretching the skin before performing the punch biopsy allows the relaxed skin defect to appear more elliptical and makes it easier to close. The skin is stretched perpendicular to the relaxed skin tension lines, so that the resulting elliptical-shaped wound and closure are parallel to these skin tension lines. Punch biopsy of inflammatory dermatoses can provide useful information when the differential diagnosis has been narrowed. Cutaneous neoplasms can be evaluated by punch biopsy, and the discovery of malignancy may alter the planned surgical excision procedure. Routine biopsy of skin rashes is not recommended because the commonly reported nonspecific pathology result rarely alters clinical management.