PURPOSE: To determine the rates at which normal ovaries in women of reproductive age were observed at MRI, as well as differences in the size of a normal ovary and follicles, and the number of follicles, according to age. MATERIALS AND METHODS: The MRI findings in 46 patients with normal ovaries were retrospectively analysed and proven grossly at surgery and/or pathologically. The detection rate and size of the ovaries, and the number of follicles and size of the largest were determined, and differences were analyzed according to age: under 30, 30-39, and 40 years or over. RESULTS: Among 46 patients, bilateral ovaries were detected in 39 and unilateral ovary in seven. The overall detection rate was 92.4% (85/92), varying according to age. It was 100% (18/18) in those aged under 30, 95% (38/40) in the 30-40 age group, and 85.3% (29/34) among those aged 40 or over. Ovary size ranged between 15 and 50 (average, 24.3) mm and was most commonly 20-30 mm, regardless of age (60%). The average size was 28.8 mm under 30 years of age, 25.3 mm between 30 and 39, and 20.3 mm at age 40 or over (p<0.01). The number of follicles was recorded as 2, 3, 4, or 5 or more, with 10.6%, 23.5%, 18.8% and 47.1% of patients, respectively, assigned to these categories. Among those aged 30-39, ovaries containing five or more follicles were most common, with 83.3% of those under 30 and 47.4% of those aged 30-39 falling into this category. Among patients aged 40 or over, only 24.1% of ovaries contained five or more follicles; most (37.9%) contained three (p<0.05). The size of the largest follicle ranged from 2 to 30 mm and, regardless of age, 5-10-mm follicles were most common (43.5%). There were no significant differences according to age. CONCLUSION: MRI is a useful tool for detecting normal ovaries in women of reproductive age. We found that most normal ovaries were 20-30 mm in size and contained five follicles or more, the largest follicle being 5-10 mm. The size of an ovary and the number of follicles decreased significantly with age.