As required by section 1839 of the Social Security Act, this notice announces the monthly actuarial rates for aged (age 65 or over) and disabled (under age 65) enrollees in the Medicare Supplementary Medical Insurance (SMI) program for 1999. It also announces the monthly SMI premium rate to be paid by all enrollees during 1999. The monthly actuarial rates for 1999 are $92.30 for aged enrollees and $103.00 for disabled enrollees. The monthly SMI premium rate for 1999 is $45.50. (The 1998 premium rate was $43.80). The 1999 Part B premium is not equal to 50 percent of the monthly actuarial rate because of the differential between the amount of home health that is transferred into Part B in 1999 (two-sixths) and the amount in Part B that is included in the premium calculation (two-sevenths).