A method of full-wave analysis is used to compute the theoretical values of reflexion and conversion coefficients of long and very long radio waves incident on a horizontally stratified ionosphere having a postulated height distribution of electron concentration and collision frequency. With reasonable values of collision frequency ($\S$4 and figure 1), the electron distribution is then progressively changed until the computed values of the reflexion parameters agree with experimental measurements over a range of frequencies from 16 to 100 kc/s at both steep and oblique mcidence. Height distributions of electrons which would explain the results of experiments made at different times of the day, the year, the solar cycle, and during an eclipse, are presented in figures 2 to 7. It is shown that these distributions are consistent with a wide range of experimental results on other frequencies. Important structural features in the electron distribution are noticed: by day (figure 2) there is a small peak of electron concentration near 64 km, a sharp gradient near 74 km, and a shallow gradient in the height range 75 to 88 km which joins the bottomside of the E-layer; at night (figure 7) electron concentrations below 80 km are very small, and there is a sharp gradient near 90 km. The electron concentrations above and below 70 km depend in different ways on the intensity of solar radiation.