The data used in this study was collected by the original MEDEX project in Seattle, Washington. The original use of the data by the project was to measure changes in patient characteristics. The MEDEX-dcsigned data collection system is compared with proposed systems for collecting nationwide ambulatory health care data and found to be very similar. Hence, the success of the MEDEX data collection effort is additional evidence that such data can be collected on a large scale, if the physicians and their ancilliary personnel are properly motivated.Analysis of the data yielded distributions such as patient age, sex, age by sex, diagnosis and dispositions, as well as the distributions of dispositions by diagnosis. These distributions are based on reports from over 11,000 physicianpatient contacts during the summers of 1969 and 1970 by seven physicians in five rural practices located in eastern Washington State. These results are shown for each of the practices individually and for the combination of all practices, with the exception that the dispositions by diagnosis distributions are prepared for the combined practices only. Where appropriate, the results of this study are compared with the findings of Last and White4and these results generally substantiate their findings. When differences are noted, explanations are proposed to account for the differences.