Background: Perineural invasion (PNI) is an important factor may possibly influence the aggressiveness of basal cell carcinoma (BCC). Objective: Our purpose was to evaluate the incidence, features, and outcomes of BCC with PNI in patients treated with Mohs micrographic surgery (MMS). Method: This prospective, multicenter case series included all patients in Australia treated with MMS for BCC with PNI, who were monitored by the Skin and Cancer Foundation Australia between 1993 and 2002. The parameters recorded were patient demographics, reason for referral, duration of tumor, site, preoperative tumor size, recurrence before MMS, histologic subtypes, postoperative defect size, and recurrence at 5 years after MMS. Results: Two- hundred eighty- three patients were diagnosed with PNI. Most cases occurred in male patients (61% ; P=.006) and in previously recurrent tumors (60.4% ; P < .001). The infiltrating, morpheic, and basosquamous subtypes were more likely to be associated with PNI (P < .0001). Tumor sizes before excision and postoperative defect sizes were significantly larger in cases with PNI compared with cases with no PNI (P < .001 for both parameters), as was the mean number of Mohs excision levels. Seventy- eight patients completed a 5- year follow- up period after MMS, and 6 of them (7.7% ) were diagnosed with recurrence.Limitations: Data were missing for some outcome measures. Conclusion: PNI is an uncommon feature of BCC. When present, PNI is associated with larger, more aggressive tumors, and the risk of 5- year recurrence is higher. This emphasizes the importance of tumor excision with margin control and long- term patient monitoring. Objective: Our purpose was to evaluate the incidence, features, and outcomes of BCC with PNI in patients treated with Mohs micrographic surgery (BCC). Background: Perineural invasion (PNI) is an important factor that may influence the aggressiveness of basal cell carcinoma MMS). Method: This prospective, multicenter case series included all patients in Australia treated with MMS for BCC with PNI, who were monitored by the Skin and Cancer Foundation Australia between 1993 and 2002. The parameters recorded were patient demographics, reason for referral, duration of tumor, site, preoperative tumor size, recurrence before MMS, histologic subtypes, postoperative defect size, and recurrence at 5 years after MMS. Results: Two- hundred eighty- three patients were diagnosed with PNI. 61%; P = .006) and in previously recurrent tumors (60.4%; P <.001). The infiltrating, morpheic, and basosquamous subtypes were more likely to be associated with PNI (P < .0001). Tumor sizes before excision and postoperative defect sizes were significantly larger in cases with PNI compared with cases with no PNI (P <.001 for both parameters), as was the mean number of Mohs excision levels. Seventy- eight patients completed a 5- year follow-up period after MMS, and 6 of them (7.7%) were diagnosed with recurrence. Limitations: Data were missing for some outcome measures. Conclusion: PNI is an uncommon feature of BCC. When present, PNI is associated with emphasized, the more aggressive tumors, and the risk of 5-year recurrence is higher. This emphasizes the importance of tumor excision with margin control and long-term patient monitoring.