Cancer mortality rates for 1979-81 among Puerto Ricans and non-Hispanic whites in New York City are analyzed for cancer in six sites. They include cancers of the lung, esophagus, breast, stomach, colon, ovary, and all cancers. New York City health areas were divided into four quartiles representing four levels of income. In general, Puerto Ricans in New York City have lower mortality rates from cancer than non-Hispanic white residents of the city. In comparing cancer mortality by quartile, Puerto Rican males show little variation. Puerto Rican females show their highest mortality rates from breast cancer in the wealthiest quartile, and non-Hispanic white women show highest mortality rates from breast cancer in the poorest quartile. Non-Hispanic white males show mortality rates from lung cancer in the poorest quartile that are distinctly higher than in the more affluent ones. For all groups, with the exception of Puerto Rican males, mortality rates from all cancers increased progressively with decreasing income. Factors influencing differential mortality rates by quartile appear to include tobacco use, alcohol consumption, occupational hazards, fertility, and differential use of health facilities.