Traditional sampling techniques have not yielded desired results when applied to
hidden or rare populations. A hidden population of considerable interest in Nigeria is
that of students in tertiary institutions engaged in substance abuse because of the
stigma surrounding such habits and the high heath-risk they constitute to both
themselves and the communities where they are found. Earlier works on the subject
have concentrated on descriptive approaches. This paper uses the Horvitz-Thompson
network sampling technique to estimate the proportion of students in tertiary
institutions in Lagos who partake in substance abuse.