This report presents a chronological overview of the status of respirable dust exposures in underground and surface bituminous coal mines since inception of the 1969 Federal Coal Mine Health and Safety Act. Data for various intervals from 1970 through 1977, are presented for selected mining operations. Comparisons are made using data available from the mine operators' sampling program and from MSHA surveys. The data demonstrate the marked decrease that has occurred in respirable dust exposures since inception of the 1969 Act.