To systematically review the literature on the relationship between early childhood low income/socioeconomic status (SES) and physical health in later childhood/adolescence, to identify gaps in the literature and to suggest new avenues for research. A systematic search of electronic databases from their start date to November 2011 was conducted to identify prospective longitudinal studies in industrialized countries with a measure of low income/SES in the first 5 years of life and physical health outcomes in later childhood or adolescence. STROBE criteria were used to assess study quality. Risk estimates were expressed as odds ratios with 95 % confidence intervals where possible. Heterogeneity of studies precluded meta-analysis. Nine studies fulfilled the inclusion criteria. Significant associations of early childhood low income/SES with activity-limiting illness, parent-reported poor health status, acute and recurrent infections, increasing BMI percentile and hospitalization were reported. Results for parent-reported asthma were less consistent: there was a significant association with low income/SES in early childhood in 2 studies but null findings in 3 others. This systematic review of the association of early childhood low income/SES with physical health status in later childhood and adolescence shows that, in contrast to the extensive literature on the impact of poor childhood social circumstances on adult health, the evidence base is limited. The literature points to some associations of early low income/SES with later poor health status, but many key research questions remain unanswered. Implications for further research are considered.