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Response to epidermal growth factor receptor inhibitors is poorer among stage IV colorectal cancer (CRC) patients with KRAS mutations; thus KRAS testing is recommended before treatment. KRAS testing was collected by Surveillance, Epidemiology, and End Results (SEER) registries for 2010 CRC cases, and our goal was to provide the first population-based estimates of testing in the United States.SEER CRC cases diagnosed in 2010 were evaluated (n=30,351). χ2 tests and logistic regression were conducted to determine patient characteristics associated with KRAS testing, stratified by stages I-III versus stage IV. Log-rank tests were used to examine survival by testing status.KRAS testing among stage IV cases ranged from 39% in New Mexico to 15% in Louisiana. In the model, younger age, being married, living in a metropolitan area, and having primary site surgery were associated with greater odds of receiving KRAS testing. Those who received testing had significantly better survival than those who did not (P<0.0001). Among those who received testing, there was no significant difference in survival by mutated versus wild-type KRAS. Five percent of stage I-III cases received testing.Wide variation in documented KRAS testing for stage IV CRC patients exists among SEER registries. Age remained highly significant in multivariate models, suggesting that it plays an independent role in the patient and/or provider decision to be tested. Further research is needed to determine drivers of variation in testing, as well as reasons for testing in stage I-III cases where it is not recommended.