The 1-8A band of synodic full-disc solar X-rays (1-8A) W/m(2) were measured nearly continuously from 1975 to 1981 aboard the SMS-1, SMS-2, GOES-1, GOES-2, and GOES-3 satellites. The 1-8A band of X-rays are proportional to the emission measure at coronal heights at temperatures greater than 2,000,000 K. A practical method of describing solar 1-8A mean and background X-ray measurements in a continuous time series to describe long-term solar variability is discussed. Intercomparisons of the satellites using linear regression techniques and a useful background coronal index are described. Sources of error and statistical information on relative accuracy are discussed. Data are presented in monthly plots of hourly averages, in tables of daily mean and background indices, and in comparison to the Ottawa 10.7 cm radio flux.