This study examines the prevalence and determinants of adolescents' unintended pregnancy and induced abortion in Owerri, Nigeria. A pre-coded questionnaire was used to obtain information from 540 female adolescents of mean age 15.8 years. In addition, four FGDs were held with female adolescents in selected localities and in-depth interviews held with fifteen health-care service providers. Almost all the adolescents (99.8%) were Christians, with 70.3% being Catholics and 68.2% living with their parents. Over half (57.2%) of the adolescents had had sex. Contraceptives were rarely used owing to deep-seated cultural values. The data show that 31.6% of those who had ever had sex had an unintended pregnancy. Of these, 78.9% had recurrent pregnancies and 20.2% had an abortion. Of the latter, 41.8% had a recurrent abortion and 72.7% a post-abortion problem, for which 70.2% never sought treatment, increasing the risk of infertility in later life. The abortion seekers mostly went to patent medicine operators. A more acceptable and cost-effective contraceptive campaign involving use of local vernacular and traditional/local opinion leaders should be explored.