The objective of this Bureau of Mines research work was (1) to determine how well the E. I. Dupont de Nemours & Company P-2500 personal dust sampling pump controls the flow rate at 2 l/min and (2) to compare respirable dust measurements made using the p-2500 with those made using a nonpulsating sampling flow system, both using the dorr-oliver 10-mm nylon cyclone dust size classifier. The calibrator and the operation manual for the p-2500, supplied by the manufacturer, were also evaluated. Flow tests consisted of long- term (6- to 8-hour) flow stability tests at various backpressures, a low-flow indicator examination, flow controller response time tests, and pulsation tests. Dust tests were performed using coal, silica, and Arizona road dust. No tests were performed to examine effects of temperature, barometric pressure, vibration, or mechanical shock. These pumps performed well within manufacturer specifications in all tests.