Mikulicz's disease, a disorder known for more than 100 years, characterized by dacryoadenitis and enlargement of submandibular glands, is now recognized as a classic IgG4-related condition, called IgG4-related dacryoadenitis (DA) and sialoadenitis (SA). We report a patient with massive submandibular gland enlargement. No properly diagnose had been made after more than 10 times of hospital visits and 3 times of localized tumor resection in various hospitals during the last 3 years. To confirm the diagnosis, an extended biopsy of the submandibular gland was made and the histological findings were consistent with the manifestation of IgG4-related Sialoadenitis (IgG4-SA). Only two sessions of X-ray radiation therapy were applied, then the glandular enlargement was completely subsided in 3 weeks. No corticosteroids nor other immunosuppressive agents was used for the treatment. During 10 years follow-up no recurrence was noticed.