In a study to investigate the characteristics of the "Unbooked mother", the medical records of 467 patients who presented for delivery with no prenatal care at the obstetric unit of the King Khalid University Hospital (KKUH), Riyadh, during the period 1991 to 1995 were evaluated. For controls, the records of 415 mothers who had pre-natal care in the Unit over the same period were also evaluated. Data pertaining to their socio-demographic characteristics, previous obstetric history, prevalence of pregnancy-related and familial diseases, gestation age at delivery and weights of the babies, were extracted and analysed using odds ratios and 95% confidence intervals (C.I.). The unbooked mother tended to be young (< or = 24 years), unskilled worker, or student. On the other hand, the booked ones tended to be primigravid, with pregnancy-related (PET) and familial diseases (hypertension and diabetes). However, the level of parity, gestation age and birth weights did not appear to significantly influence the tendency to be booked or unbooked. These findings highlight the group of women who should be targeted for health education counselling regarding the value of prenatal care. This way, one can avoid some of the catastrophes often said to be associated with deliveries in the unbooked mother.