In the United States, hospital admissions for conditions sensitive to primary care are related to socioeconomic characteristics. The authors compare the prevalence of avoidable hospital admissions and their relationship to socio-economic and primary care characteristics in Spain and the United States. A case-control analysis of the relationship between avoidable hospitalizations and socioeconomic characteristics (illiteracy, unemployment, income) and primary care characteristics (type of physician and facilities for primary care) of children's area of residence was conducted in Spain. Bivariate statistical tests and conditional logistic regression were used to test the strength of the association among the variables, and to calculate the probability of being admitted to hospital for treatment of an ambulatory care sensitive (ACS) condition. Neither socioeconomic nor primary care characteristics affected this probability, and the rate of admission for ACS conditions was lower in Spain than in the United States. The provision of universal financial access to care and the availability of a consistent and accountable primary care provider are associated with lower hospitalization rates for conditions that are preventable with good primary care.