OBJECTIVE: To ascertain the relation of men's lifelong class status (as measured by neighborhood income) to the rates of early (< 34 weeks) and late (34-36 weeks) preterm birth (PTB). METHODS: Stratified and multilevel, multivariable binomial regression analyses were computed on the Illinois transgenerational birth-file of infants (born 1989-1991) and their parents (born 1956-1976) with appended U.S. census income information. The median family income of men's census tract residence at two-time periods were utilized to assess lifelong class status (defined by residence in either the lower or upper half of neighborhood income distribution). RESULTS: In Cook County Illinois, the preterm rate for births (n = 8115) to men with a lifelong lower class status was twice that of births (n = 10,330) to men with a lifelong upper class status: 13% versus 6.0%, RR = 2.2 (2.0, 2.4). This differential was greatest in early PTB rates: 3.9% versus 1.4%, RR = 3.0 (2.5, 3.7). The relation of men's lifelong class status to both PTB components persisted among non-teens, married, college-educated, and non-Latina White women, respectively. The adjusted (controlling for maternal demographic characteristics) RR of early and late PTB for men with a lifelong lower (versus upper) class status were 1.4 (1.1, 1.9) and 1.2 (1.0, 1.4), respectively. The population attributable risk of early PTB for men's lifelong lower class status equaled 16%. CONCLUSIONS: Men's lifelong lower (versus upper) class status is a novel risk factor for early preterm birth regardless of maternal demographic characteristics. This intriguing finding has public health relevance.