This chapter investigates the effect of health visitors on infant and child health using the notifications of birth and visiting records created by health visitors in the county of Derbyshire. In reflection of the permissive nature of the national legislation, health visiting in Derbyshire developed in a piecemeal fashion, some of the district councils has taken it up in response to the Act, and others only following suit after the countywide adoption prompted by the 1915 Act. Systematic analysis of the effect of health visiting on individuals is complicated by the fact that health visitors, in their attempts to improve survival, concentrated on those they felt were at highest risk of death; the poorest in particular. The fundamental aspect of health-visiting success, however, was the facility to visit mothers while their babies were still very young: this was the very reason for notification of births legislation, the corner-stone of health visiting.