Abstract Density scale heights, H ϱ , are derived by a new method, which utilizes the spin decay of paddlewheel satellites in highly eccentric orbits. The results are compared with H ϱ obtained by other satellite methods, and with those given by the Harris and Priester 1964 Model Atmosphere. Equations are derived for the calculation of H ϱ from spin decay and X-ray absorption. The gradient of H ϱ is calculated for the first time from the drag on a single satellite (IMP 2). Although the trend with solar activity can be seen clearly in the best data, the most obvious conclusion is that it is, in general, very difficult to determine density scale heights accurately. The best method so far developed for obtaining annual averages is the method of King-Hele. The best method of obtaining averages over a few days is to use the spin decay of paddlewheel satellites in highly eccentric orbits. The accuracy of these two methods appears to be 5–10%, if the possible variation in drag coefficient is ignored.