Trends in respirable dust concentration in coal mines with longwall or continuous miner sections were examined. Data collected during fiscal year 1978 and 1983 through 1987 from mines with either continuous or longwall mining sections or both for determining compliance with the respirable coal dust standard, 2.0mg/m3 were analyzed. In fiscal year 1987 about 65% of the mines in the United States used continuous mining sections. Since fiscal year 1978 production from longwall panels increased from 500 tons per shift to 2200 tons/shift in 1987. From fiscal year 1983 through 1987, 260,370 respirable coal dust samples were collected in continuous mining operations. These had an arithmetic mean dust concentration of 1.0mg/m3. Overall 12.2% of the samples exceeded the standard. The arithmetic mean coal dust concentration in samples for fiscal year 1978 was 1.4mg/m3. In fiscal year 1987, 432 continuous mining sections were cited for noncompliance with the standard once; 120 were cited at least twice. During 1983 through 1987, 12,622 samples were collected from longwall mining operations. The arithmetic mean respirable dust concentration in these samples was 2.0mg/m3, 36.8% being out of compliance with the standard. In fiscal year 1978 the arithmetic mean dust concentration in longwall mining samples was 2.5mg/m3, 51.6% being out of compliance with the standard. The decrease in mean dust concentration between 1978 and 1987 was statistically significant. In fiscal year 1987, 58 longwall mining sections were cited once for being out of compliance, 31 at least twice. Data from ten mines having both continuous and longwall mining sections indicated arithmetic mean dust concentrations of 1.2 and 2.1mg/m3, respectively, for these operations. The authors conclude that longwall mining operations are associated with more serious respirable dust problems than continuous mining operations.