A practice analysis is a tool that bridges knowledge and clinical performance into a format that permits assessment. For physician assistants (PAs), this contributes to a psychometrically sound examination administered by the National Commission on Certification of Physician Assistants (NCCPA). The 2004 practice analysis of 5,282 completed PA surveys (13.4% out of 39,517 sent) was representative of the PA population in years experience, geographical distribution, and practice specialty. The survey revealed 8 content domains with formulating the most likely diagnosis, basic science concepts, and pharmaceutical therapeutics as the three skills needed for most scenarios. The data were also analyzed by patient acuity (acute limited, chronic progressive, life-threatening emergency). As a result, NCCPA's test item pool and content blueprint for assessing core knowledge of American PAs on the Physician Assistant National Certifying Examination (PANCE) and the Physician Assistant National Recertifying Examination (PANRE) has been enhanced.