Socioeconomic inequalities cause more disease and death than most risk factors, especially in cities. This systematic review of the scientific evidence included articles in English, Spanish, Portuguese, and Italian and excluded studies with low levels of evidence and those that did not analyze associations between mortality and socioeconomic status in urban settings. Articles were selected by two independent reviewers, and data extraction used evidence tables. A total of 1,509 records were obtained, and 24 were included. All the studies showed higher mortality rates in poorer areas. Six studies showed an association with cardiovascular diseases, four with lung diseases, and three with AIDS, infectious and parasitic diseases, and cirrhosis. The selected studies showed low consistency in the results and important methodological limitations that prevented comparisons between studies or the extraction of relevant conclusions.