Over the past 12 months, approximately 17,500 blood samples and over 1,000 breath samples were collected from blood donors at 13 major sampling locations throughout the nation. Two of these locations were revisited, so that a total of 15 separate sampling programs have been conducted. Samples collected from the Milwaukee area before the initiation of the COHb Mass Screening Program have been combined with those of the regular Milwaukee study to form a detailed written report. Data from five other cities, New York, Miami, St. Louis, Chicago and Washington, D. C. have undergone preliminary computer analysis. A manual analysis of lab tabulated data has also provided up-to-data information on non-smokers for all of the sampling sites and cities thus far visited.