We describe a 61 year-old caucasian male diagnosed with rheumatoid arthritis. He was started on methylprednisolone pulses because of a severe flare of symmetric polyarthritis while he was on weekly intramuscular methotrexate and low-dose oral prednisone. After the second pulse of methylprednisolone the patient suddenly developed severe abdominal pain with free air under the right hemidiaphragm in the chest roentgenogram. The emergency surgery revealed the perforation of a colonic diverticulum. We suggest that methylprednisolone pulses should be carefully used in those patients over 50 years of age and/or people with demonstrated or suspected diverticular disease.