This study aims to evaluate the long-term outcome of major salivary gland adenocystic carcinoma (ACC). This is a retrospective review of 54 cases of ACC during a 35-year period from 1974 to 2009 at the Helsinki University Central Hospital, Helsinki, Finland. Medical records and histological samples were reviewed. All patients had a minimum follow-up time of 5 years or until death. Most of the tumours occurred in the parotid gland (n = 30, 56 %) followed by submandibular gland (n = 22, 41 %) and sublingual gland (n = 2, 4 %). Fifty-two patients (96 %) were treated with curative intent. All of these patients except one were primarily treated with surgery, and 29 patients (54 %) also received postoperative radiotherapy for their primary tumour. Two patients (4 %) received palliative radiotherapy. For those treated with curative intent, 32 patients (62 %) had disease recurrence. Twenty-four patients (75 %) had their first disease recurrence within 5 years and eight patients (25 %) later than 5 years. The difference in the length of recurrence-free time interval (<5 vs. >5 years) had a significant impact on 5-year overall survival (OS) and disease-specific survival (DSS). The OS, DSS and disease-free survival (DFS) across stages I-IV varied between 46-100, 50-100 and 46-100 %, respectively. Age over 45 years, T stage, and presence of neck metastases had a significant negative prognostic effect. More than half of the patients had recurrent disease. An extended follow-up for these patients seems feasible as most of the distant metastases were detected within a 10-year period.