The health effects of diesel exhaust, especially particulate, are a concern in the underground workplace. Diesel particulate matter (dpm) contains compounds that are mutagenic; some are known carcinogens. While coal dust has been an important health concern for a number of years, the concern about dpm is more recent. A means of measuring the concentration of dpm is prerequisite to the effective control and reduction of dpm. At the present time, there is no fully proven method to distinguish between diesel and coal particulate. In this research, the laser raman quantitative analysis (lrqa) method is applied to determine the amounts of respirable diesel and coal on a filter containing airborne particulate matter. Particulate samples were obtained during 1 week of underground air sampling work in August 1987 in the Kerr McGee Galatia Mine. The particulate samples were collected using gravimetric personal samplers, a method similar to that used by U.S. mines to determine the airborne respirable coal dust concentrations. Results from the lrqa method are compared with those from the size- selective sampling method.