The dearth of quantitative evidence of customary gender discrimination in late 19th and early 20th century Britain is puzzling, particularly in light of the qualitative evidence which suggests that pro-male bias existed above and beyond what might be expected as a strategic response to males’ greater neonatal fragility and relatively superior labor market prospects. Using new longitudinal infant medical data from turn-of-the-century London, we investigate whether child gender played a role in the quality and quantity of investment in human capital. We find significant differences by infant gender in catch-up growth and parental effort associated with clinic attendance, although the evidence of systematic gender bias in other metrics is limited. Results suggest that girls need to suffer poorer health than their male counterparts before they are brought to clinic, and that at a given level of health, boys’ parents tend to travel farther to visit the clinic than do those of girls, although this male premium manifests only for longer home-to-clinic distances. Together, these facts suggest that while parents put more effort into promoting the health of their sons than daughters, such bias may have only manifested under extreme circumstances. This finding may help explain why gender discrimination has been difficult to substantiate in everyday contexts both historically and in today’s developing countries.