To assess psychometric properties of a recently-designed medical-homeness instrument, the Medical Home Attributes Scale (MHAS), we surveyed clinical practices with NCQA recognition as medical homes. Exploratory factor-analyses of the 25 clinician-rated MHAS items from 228 practices revealed four underlying factors: clinical team interactions, record review/documentation, reviewing patient needs, and quality improvement/monitoring. In multivariable regressions, MHAS scores were 8.5 points higher for multispecialty practices vs. primary-care only practices, and were 5.5 points lower for hospital-owned practices vs. other ownerships. The MHAS, a brief measure of medical-homenness of clinician practices, is highly reliable and sensitive to differences in practice specialty and ownership.