OBJECTIVES: To examine the proportion, geographic variation, and predictors of infant hospital readmission within 6 weeks of the postbirth discharge. METHODS: A cross-sectional, population-based study was conducted of all infants who were born from 1997 through 2001, linkable to the birth mother, and discharged alive from the hospital (N = 68 681) using hospital discharge files in the Canadian province of Manitoba. The following predictors of readmission were examined using logistic regression: preterm, low birth weight, neighborhood income, geographic location (the North, Rural South, and Urban areas of Winnipeg and Brandon), breastfeeding status, length of stay, maternal age, and type of delivery. Using 9 non-Winnipeg regions and 12 Winnipeg subregions, ecologic correlations (1-tailed Spearman) between newborn hospital readmission rates and the following were examined: 1) a region's overall health status, measured by the premature mortality rate (PMR), or death before aged 75 years and 2) a region's socioeconomic risk, using the Socio-Economic Factor Index (SEFI). RESULTS: The proportion of infants who were readmitted to the hospital at least once within 6 weeks of postbirth hospital discharge was 3.95%, with respiratory illness the leading cause (22.3% of readmissions). Risk of readmission was higher for infants who were born preterm (adjusted odds ratio [AOR]: 1.80; 95% confidence interval [CI]: 1.55-2.10), who were of the 3 lowest income quintiles (lowest: AOR: 2.02; 95% CI: 1.77-2.32; low: AOR: 1.48; 95% CI: 1.29-1.71; middle: AOR: 1.26; 95% CI: 1.08-1.47), who resided in the North (AOR: 1.85; 95% CI: 1.66-2.07) or Rural South (AOR: 1.25; 95% CI: 1.14-1.36), who were not breastfed (AOR: 1.32; 95% CI: 1.20-1.44), whose mother's age was 17 or younger (AOR: 1.30; 95% CI: 1.10-1.55), whose mother was 18 to 19 years of age (AOR: 1.25; 95% CI: 1.09-144), or who were born by cesarean section (AOR: 1.30; 95% CI: 1.19-1.43). Regional readmission rates were correlated with PMR (9 non-Winnipeg regions: r = 0.77 for PMR and r = 0.68 for SEFI; 12 Winnipeg Community Areas: r = 0.49 for PMR and r = 0.73 for SEFI). CONCLUSIONS: Income and geography are strongly associated with newborn hospital readmission. Modifiable risk factors include increasing breastfeeding rates, decreasing cesarean section rates, and decreasing adolescent pregnancy rates (or increasing adolescent parental support), but these need additional study to establish causation.