To clarify the natural history of fundic gland polyposis (FGP) without familial adenomatosis coli (FAC). Thirty-one FGP patients without FAC (six men and 25 women) were followed up with radiography and endoscopy for 1-13 years (mean, 4.3 years). In eight of 11 patients who initially had a single polyp, the polyp disappeared, probably due to endoscopic forceps biopsy. Of 20 patients with multiple polyps, seven (one man and six women with a mean age of 40.6 years at initial diagnosis) had obvious changes in the number of polyps, including complete disappearance in three patients, a decrease in one, transient disappearance followed by recurrence in two, and an increase in one. These patients were younger and had a greater number of polyps at initial diagnosis than the remaining 16 patients without any remarkable change. FGP without FAC is characterized by spontaneous decrease or increase in the number of polyps, especially in middle-aged female patients with a large number of polyps.