Objectives: To present a large series of patients with orbital invasion by per iocular basal cell carcinoma (BCC). Design: Retrospective, noncomparative, inter ventional case series. Patients: All cases diagnosed with orbital invasion by pe riocular BCC between January 1985 and July 2004 in 3 Orbital Units in Australia. Methods: The clinical records of all patients were reviewed. Main Outcome Measu res: Patients’demographics, clinical presentation, histologic subtypes, treatme ntmodalities, recurrence rate, and tumor-related death. Results: There were 64 patients (49 males) with a mean age of 70±13 years. Most tumors (84.4%) were r ecurrent or previously incompletely excised, and the medial canthus was most fre quently involved (56.2%). Signs suggestive of orbital involvement included a ma ss with bone fixation (35.7%), limitation of ocular motility (30.4%), and glob e displacement (17.6%). There were no signs suggestive of orbital invasion in 3 5.7%. Most patients (51.6%)-had infiltrative histologic findings, and perineu ral invasion was present in 19.3%. Treatment modalities were mainly exenteratio n alone or combined with radiotherapy. During a mean follow-up period of 3.6 ye ars, 3 cases of recurrence (4.7%)were diagnosed. Only 1 patient (1.6%) died fr om tumor-related causes. Conclusions: Orbital invasion by periocular BCC is an uncommon event that may be associated with significant ocular morbidity and, rar ely, death. Because orbital invasion may often be clinically silent, clinicians need to be alert to the possibility in high-risk tumors and consider appropriat e imaging. Surgical treatment with exenteration or excision, with or without rad iotherapy, results in a low recurrence and mortality rate. Objectives: To present a large series of patients with orbital invasion by periocular basal cell carcinoma (BCC). Design: Retrospective, noncomparative, interventional case series. Patients: All cases diagnosed with orbital invasion by pe riocular BCC between January 1985 and July 2004 in 3 Orbital Units in Australia. Methods: The clinical records of all patients were reviewed. Main Outcome Measures: Patients’ demographics, clinical presentation, histologic subtypes, treatme ntmodalities, recurrence rate, and tumor-related death. Results: There were 64 tumors (84 males) with a mean age of 70 ± 13 years. Most tumors (84.4%) were r ecurrent or previously incompletely excised, and the medial canthus were most fre quently involved (56.2%). Signs suggestive of orbital involvement included Most patients (51.6%) - had a disease with ocular motility (30.4%), and glob e displacement (17.6%). infiltr ative histologic findings, and perineu ral invasion was present in 19.3%. During a mean follow-up period of 3.6 ye ars, 3 cases of recurrence (4.7%) were diagnosed. Only 1 patient (1.6%) died fr om tumor-related causes. Conclusions: Orbital invasion by periocular BCC is an uncommon event that may be associated with significant ocular morbidity and, rar ely, death. Because orbital invasion may often be clinically silent, clinicians need to be alert to the possibility in high-risk tumors and consider appropriat e imaging. Surgical treatment with exenteration or excision, with or without rad iotherapy, results in a low recurrence and mortality rate.