The aim of this study was to describe the effects of sociodemographic factors and maternity ward practices on the duration of breastfeeding in Swedish primiparas (n = 194) and multiparas (n = 294), consecutively selected from hospital birth files for 3 months, who responded to a questionnaire 9 to 12 months after childbirth. The impact of sociodemographic data and maternity ward practices on exclusive and any breastfeeding were examined. Smoking and supplementation without medical reasons influenced the duration of both exclusive and any breastfeeding negatively, whereas early first breastfeeding influenced the duration of both exclusive and any breastfeeding positively, and parity had no significant influence. Late hospital discharge influenced the duration of exclusive breastfeeding positively, and higher maternal age influenced the duration of any breastfeeding positively. These variables altogether explained 11.4% (P < .001) of the variance in the duration of exclusive breastfeeding and 8.2% (P < .001) of the duration of any breastfeeding.