Background: In adults with insulin-treated diabetes, self-monitoring of blood glucose (SMBG) rates may be lower in minority or low-income populations, but the effect of income on racial/ethnic differences in SMBG is unknown. Methods: We assessed whether racial/ethnic differences in SMBG vary by income among adults with insulin-treated diabetes by using Behavioral Risk Factor Surveillance System data from 2000 through 2004. We measured the prevalence of SMBG at least once per day among 16,630 adults aged ≥19 years with insulin-treated diabetes. Results: At incomes ≥$20,000, Hispanics and non-Hispanic Blacks reported similar but lower SMBG rates than did non-Hispanic Whites (78%, 77%, 85%; P ≤ .01). However, among those with income ≤$20,000, Hispanics performed SMBG substantially less than did Blacks or Whites (65%, 79%, 85%; P ≤ .01). Racial/ethnic differences in SMBG persisted after adjustment for age, sex, education, health insurance, health status, survey period, and diabetes measures. Receipt of diabetes education varied significantly by race/ethnicity in the income <$20,000 group only (Hispanics 49%, Blacks 64%, Whites 62%; P < .001). Low-income Hispanics with limited English proficiency had lower SMBG and diabetes education rates than did those with English proficiency (61% vs 79% and 44% vs 58%, respectively). Conclusions: Among US adults with insulin-treated diabetes, Hispanics and Blacks performed daily SMBG less frequently than did Whites. Stratification by income revealed a disparity gradient in the income <$20,000 group: SMBG rates decreased from Whites to Blacks to Hispanics. Low-income Hispanics with limited English proficiency are at greater risk for reduced SMBG than are those proficient in English.