The primary objective of the study was to determine the extent of pre- and extra-marital sexual involvement of married males of slums. Data were collected through a sample survey and in-depth interviews. The respondents were low-income married male household heads living in slums of Bangladesh. The systematic random sampling technique was used for selecting the respondents. A total of 408 male samples were drawn from a slum of about 10, 000 households. During the survey, resource persons were identified for in-depth interviews. A total of 37 in-depth interviews were conducted. A total of 89% of the respondents admitted having some kinds of pre-marital sexual experiences and about 81% of them had pre-marital intercourse. Among the respondents with pre-marital sex experience, about 63% of them had sexual intercourse with female sex workers. Over 26% of the respondents with pre-marital sex experience had intercourse with their unmarried first cousins before marriage. Nearly 37% of the respondents with premarital sex experience had intercourse with fictive kin. About 66% of the total sampled respondents of the study had extra-marital sexual affairs and about 55 % of them had intercourse with one or more women other than their wives. The major extra-marital sex partners were sex workers (43%), followed by fictive kin (32%), sisters-in-law (20%), and extra-marital lovers (16%). Religious distribution shows that Muslims and Hindus do not differ with regard to sexual behaviors. Although the samples of the study do not represent the entire population of the country, it definitely represents the growing lower class urban population who constitute considerable proportion of the city population. The above findings convincingly raise the question of puritan character of Bangladesh society.