Safety measure development has focused on inpatient care despite outpatient visits far outnumbering inpatient admissions. Some measures are clearly identified as outpatient safety measures when published, yet outcomes from quality improvement studies also may be useful measures. The authors conducted a systematic review of the literature to identify published articles detailing safety measures applicable to adult primary care. A total of 21 articles were identified, providing specifications for 182 safety measures. Each measure was classified into one of 6 outpatient safety dimensions: medication management, sentinel events, care coordination, procedures and treatment, laboratory testing and monitoring, and facility structures/resources. Compared to the multitude of available inpatient safety measures, the number of existing adult primary care measures is low. The measures identified by this systematic review may yield further insight into the breadth of safety events causing harm in primary care, while also identifying areas of patient safety in primary care that may be understudied.