In this hospital-based study of dementing illnesses in Ibadan, 37 cases were seen over a 6 year period from 1984 to 1989 out of 57,440 cases admitted. The average hospital frequency was 64 cases per 100,000 admissions. Eighteen cases (48.7%) had vascular dementia. The other types encountered were: secondary dementias (8), mixed (5), probable primary degenerative (1) and the remaining 5 cases were unclassifiable. The associated conditions were mainly hypertension, parkinsonism, diabetes mellitus and benign prostatic hyperplasia. The findings confirm the relative rarity of primary degenerative dementia in Nigeria and raise the possibility of prevention of the predominant type by identifying the stroke-prone individuals early and intervening.