[en] This document describes the alpha-particle calibration services offered by the Radioactivity Group of the National Bureau of Standards (NBS) (Scheduled Calibrations; 43030C and 43040C; formerly 8.2H and 8.2I). The fundamental measurement quantities are defined, the measurement approach is described (or reviewed), and the operating procedures are described from the point of view of the calibration technician or metrologist. The measurement uncertainties, and how they are estimated, are described. Methods for maintaining and assessing quality control, e.g., international comparisons, MQA programs, etc. are also briefly reviewed