Abstract Some major results of a series of extensive measurement of A 1-absorption on eight different frequencies ranging from 1.7 to 6.5 MHz made at Calcutta during the period 1966–1968 have been presented. The data have been utilised in determining the frequency exponent ‘ m’ both during normal and disturbed periods and also in separating the so called non-deviative ( B) component of absorption and E-region parameter ( C), Both B and C values exhibit diurnal, seasonal and solaractivity dependence. The zenith angle dependence of ‘ C’ is in good agreement with observed height changes in the E-region, whereas, the dependence of ‘ C’ on solar activity is possibly caused through an increase in atomic oxygen concentration with increasing solar activity. Attempts have also been made in comparing the observed variations in ‘ B’ values with those produced by the different models of production and loss processes in vogue. The comparison suggested, that the n(NO) model of Meira (1971) with the loss model of mitra (1970) is perhaps the best in explaining the observed findings. Although, in order to explain the solar activity dependence of the B-values, it was felt necessary that the ionization due to NO must increase by at least a factor of 1.5 from solar minimum to solar maximum, or a decrease in loss rate should occur.