Collagenous and lymphocytic colitis are two inflammatory conditions of the colon that are often collectively referred to as microscopic colitis. The present report describes what is believed to be the third published case of familial microscopic colitis. A 55-year-old woman who suffered from chronic diarrhea was diagnosed with lymphocytic colitis on colonic biopsy. Subsequently, her 36-year-old daughter was diagnosed with collagenous colitis. The familial occurrence of these diseases may support an immunological hypothesis for their etiology. In addition, it supports the assumption that collagenous and lymphocytic colitis are two manifestations of the same disease process rather than two completely separate entities. The familial tendency of this disease may make a case for early colonoscopy and biopsy in relatives of patients diagnosed with microscopic colitis if they present with suggestive symptoms.