SummaryBackground and objectives Recognition of CKD by primary care practitioners is essential in rural communities where nephrology access is limited. This study determined the prevalence of undocumented CKD in patients cared for in rural primary care practices and evaluated characteristics associated with undocumented CKD as well as CKD management.Design, setting, participants, & measurements A retrospective cohort study, conducted within the Oregon Rural Practice Based Research Network, consisted of 865 CKD patients with serum creatinine$1.5 mg/dl in males and $1.3 mg/dl in females and an estimated GFR,60 ml/min per 1.73 m 2 . Documentation of a CKD diagnosis and laboratory values were abstracted by chart review.Results Of CKD patients, 51.9% had no documentation of CKD. Undocumented CKD occurred more frequently in female patients (adjusted odds ratio=2.93, 95% confidence interval=2.04, 4.21). The association of serum creatinine reporting versus automating reporting of estimated GFR on CKD documentation was dependent on patient sex, years of practitioner experience, and practitioner clinical training. Hypertensive patients with documented CKD were more likely to have a BP medication change than patients with undocumented CKD (odds ratio=2.07, 95% confidence interval=1.15, 3.73). Only 2 of 449 patients with undocumented CKD were comanaged with a nephrologist compared with 20% of patients with documented CKD (odds ratio=53.20, 95% confidence interval=14.90, 189.90).Conclusions Undocumented CKD in a rural primary care setting is frequent, particularly in female patients. Depending on practitioner characteristics, automatic reporting of estimated GFR might improve documentation of CKD in this population.