This paper deals with the impact of night work from a gender perspective, through a field study at a factory employing men and women on the night shift. It is based on data for hours of sleep over the course of several weeks, socio-demographic data,, and job information, using a semi-structured interview. The methodology includes chronobiological aspects of sleep (mainly quantitative data) and workers' discourse concerning gender-related experiences in the day-to-night switch. Despite gender issues and differences in daily life, the switch is perceived quite vividly by both men and women, permeating several aspects of life, like health, leisure, studies, and intimate personal relations. Quantitative sleep analysis showed more severe effects of night work on women, especially those with children. Such sleep patterns were associated with different expectations among men and women, revealing gender issues that are essential for understanding the reality of individuals who work odd hours.