Background: Chlorhexidine umbilical cord washes reduce neonatal mortality in south Asian populations with high neonatal mortality rates and predominantly home-based deliveries. No data exist for sub-Saharan African populations with lower neonatal mortality rates or mostly facility-based deliveries. We compared the effect of chlorhexidine with dry cord care on neonatal mortality rates in Zambia. Methods: We undertook a cluster-randomised controlled trial in Southern Province, Zambia, with 90 health facility-based clusters. We enrolled women who were in their second or third trimester of pregnancy, aged at least 15 years, and who would remain in the catchment area for follow-up of 28 days post-partum. Newborn babies received clean dry cord care (control) or topical application of 10 mL of a 4% chlorhexidine solution once per day until 3 days after cord drop (intervention), according to cluster assignment. We used stratified, restricted randomisation to divide clusters into urban or two rural groups (located