The vitreous and visual acuity in 103 eyes with idiopathic preretinal macular fibrosis were examined. The vitreous was studied biomicroscopically and the follow-up course was 6 months or more. Twenty-two eyes had no posterior vitreous detachment (group 1), 4 eyes had partial posterior vitreous detachment without traction to the macula (group 2), 17 eyes had partial posterior vitreous detachment with traction to the macula (group 3), and 60 eyes had complete posterior vitreous detachment (group 4). There were significantly more eyes with a visual acuity of 0.4 or worse, decreased acuity, or macular fluorescein leakage in group 3 than in groups 1 or 4. Decreased visual acuity was found in 41% of eyes with macular fluorescein leakage, but in only 11% of eyes without macular fluorescein leakage. It is presumed that the vitreous traction to the macula and macular fluorescein leakage are closely related to the outcome of visual acuity in cases with idiopathic preretinal macular fibrosis.