The success of any sexuality education programme in the school is directly related to the expertise of teachers and their willingness to provide instructions. This study assesses the knowledge of human sexuality education among 351 secondary school teachers in Ibadan, Nigeria, and their attitude towards inclusion of sex education in the schools' curriculum. Results revealed that none of the respondents was able to define sex education adequately and 34.8% could not identify content areas of sex education for inclusion in the schools' curriculum. Surprisingly, married female teachers and those aged 40 years and above were less favourably disposed to the introduction of sex education in schools.