The voluntary portion of Medicare, known as the Supplementary Medical Insurance (SMI) Program, that includes physician's services, home health care, medical services, outpatient hospital services, and laboratory, pathology, and radiology services. All persons entitled to Medicare Part A may enroll in Medicare Part B on a monthly premium basis.

Synonyms: Medicare Part B, SMI Programs, Programs, SMI, Medicare Supplementary Medical Insurance Program, Supplementary Medical Insurance Program, Medicare, Part B, Medicare, Program, SMI, SMI Program