Recent data indicate that North Dakota lignites are similar in mercury content to subbituminous coals from Montana and Wyoming. Studies dating back to the 1970s and early 1980s had shown that North Dakota lignites contain significantly higher levels of mercury than subbituminous coals from the Powder River Basin (10.1 mg/MMBtu for lignite compared to 6.2 mg/MMBtu for subbituminous). New data suggest significantly lower mercury concentrations for both North Dakota lignites and Powder River Basin subbituminous coals. These results indicate that North Dakota lignites contain an average of 4.2 mg Hg/MMBtu, whereas Powder River Basin subbituminous coals have an average of 3.7 mg Hg/MMBtu. Thus, the two types of coal appear to be very similar in average mercury concentrations. The difference between the new and older data likely results, in part, from recent improvements in sample collection and laboratory procedures. If North Dakota lignites do have average mercury concentrations similar to those of Montana and Wyoming coals, as indicated by the recently obtained data, it is likely that fuel switching would not significantly affect mercury emissions. These results demonstrate the importance of using up-to-date information when assessing emissions at electric utilities or other sources.