Swedish twins have been followed for mortality since 1961, when the Swedish Twin Registry was formed. During the years 1%1-73 there were 1290 deaths among twins born in 1901-25. In 1156 cases the cause of death could be established from collected records and classified according to the 1965 revision of ICD. Using the review of records as the standard, rates of detection and confirmation relating to the death certificate diagnoses were calculated. It is concluded that Swedish death certificate data are fairly valid for use in epidemiological studies and mortality statistics with regard to most cancer forms, cerebrovascular disease, ischemic heart disease, bronchitis, asthma and emphysema, accidents and suicides, but not for diabetes rnellitus, alcoholism, mental diseases, rheumatic heart diseases and other heart diseases. However, in selected clinical-epidemiological studies it is often necessary to collect all available documents prior to judging the cause of death.Data on death certificates are usually the only basis for epidemiological studies on mortality. The reliability of mortality statistics is dependent on several factors, but clinical examinations in combination with autopsies are probably our best instruments for accurately establishing cause of death ( I , 14, 19,24). However, in cases of death outside hospitals, especially sudden deaths, we often have to rely upon other information in certifying the cause of death. Therefore, in order to get an adequate evaluation of the accuracy of the cause-of-death determination, we must collect all available documents

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Daily symptom rates in patients with chronic obstructive pulmonary disease and in other subjects with presumed high sensitivity to air pollution who lived near a coal-fired plant were compared with 24-hr ambient air concentrations of nitrogen dioxide, sulfur dioxide, soot, and suspended particles as well as with emissions from the plant. The mean concentrations of each of the pollutants during the 4-month study period were below 30 micrograms/m3, and no single 24-hr concentration exceeded 100 micrograms/m3. There were no consistent associations between plant emissions and pollutant levels or between these two variables and daily symptom rates. The results indicate that the coal-fired plant was not of major importance for the occurrence of acute respiratory symptoms in the surrounding population.

mortality from all causes and from all medical causes (excluding trauma) than did DZ twins. Using life-table methods, survival (i x ) functions have been computed from the accumulated data that estimate the probability of living to a specific age for the twins surviving their brothers death. These functions have been compared between MZ and DZ twins and a somewhat greater mortality was found among the MZ twins. For all MZ twins, the probability of living to a specific age was comparable to that of the DZ twins. The various measures of concordance for early total mortality and for early mortality from medical causes provide various evaluations of the genetic determination of these events.