Background: Only a few prospective studies have been published on surgical treatments for cutaneous basal cell carcinoma (BCC). Objective: Our purpose was to report the clinical findings of all patients with BCC treated with Mohs micrographic surgery (MMS) in Australia between 1993 and 2002. Method: This prospective, multicenter case series included all patients in Australia treated with MMS for BCC, who were monitored by the Skin and Cancer Foundation between 1993 and 2002. The main outcome measures were patient demographics, reason for referral, duration of tumor, site, preoperative tumor size, recurrences before MMS, histologic classification of malignancy, and postoperative defect size. Results: The study included 11,127 patients (47% females and 53% males) with a mean age of 62 years (range, 15-98 years). In 43.8% of cases BCC was a recurrent tumor. Most of the tumors (98.3%) were on the head and neck area, most commonly on the nose (39%), cheek and maxilla (16.5%), periocular area (12.7%), and auricular region (11.4%). The most common histologic subtypes were infiltrating (30.7%), nodulocystic (24.2%), and superficial (13.6%). Previously recurrent tumors were larger than primary tumors (P < .001), had a larger postexcision defect and more subclinical extension, and required more levels of excision (P < .001). Limitations: Data were missing for some outcome measures. Conclusion: This large prospective series of BCC managed by MMS is characterized by a high percentage of high-risk tumors. Most tumors were located in the mid-facial area and the histologic subtype was mainly infiltrating or nodulocystic. That previously recurrent tumors were larger and demonstrated a more extensive subclinical extension compared with primary tumors emphasizes the importance of initial tumor eradication with margin control.