OBJECTIVE Low birth weight is associated with elevated health-care costs and adverse conditions for the newborn's start to life. A variety of health problems and an impaired potential for the infant's development are known long-term effects. Only few studies have examined the role of psychosocial and socioeconomic determinants for the incidence of low birth weight, especially in Germany. The aim of our study was to test the impact of maternal socioeconomic and psychosocial characteristics as well as health behaviour on the infant's birth weight. METHODS In an exploratory case-control study we tested whether the before mentioned potential determinants of low birth weight were observed more often among cases (birth weight <2,500 g) than among controls. Standardised interviews were conducted with maternal cases and controls. RESULTS The results show that mothers in the control group more often were married or cohabiting (100% vs. 77%; p<0.05) and that they had a higher occupational status (83% non-manual vs. 54%; p<0.05). Level of education was not significantly related to birth weight. Mothers in the case group more often reported exhaustion (p<0.05) and marital problems [M=1.8 (1.1) vs. M=1.3 (0.5); p<0.05). They were characterised by a higher burden of work-strain in terms of weather conditions, heat or infiltration [M=1.7 (1.0) vs. M=1.1 (0.4); p<0.05). The available living space was slightly smaller in the case group [M=96.5 m(2) (31.5 m(2)) vs. M=118.5 m(2) (46.8 m(2)); p<0.1). CONCLUSIONS Our results confirm international studies showing differences regarding the social context of women who give birth to a child with normal or low birth weight. Apart from vertical status characteristics, marital conditions and resulting psychosocial stressors seem to have an impact.