Night-time electron density distributions are used to study ‘coupling echo’ reflections from the X = 1 level at various frequencies. Overall reflection-matrix elements R 11, R 12 (= R 21) and R 22 are calculated as functions of the variable upper height of ionospheric slabs based on the bottom of the ionosphere. At each frequency calculations are performed for various values of θ, the angle between the geomagnetic field and the vertical. Two types of coupling echoes are found. The first type, or ‘true’ coupling echoes, depend directly on the interface matrix elements, r 12 and r 21, of the elementary thin layers into which the ionosphere has been divided, near the X = 1 level. They appear in the angular range 0 < θ ≲ 2 θ c , where θ c is the angle of critical coupling, and approach a maximum near the upper limit θ ≈ 2 θ c . They are generally characterised by the three reflection-matrix elements, R 11, R 12 and R 22, being roughly equal in absolute value at the X = 1 level. For much higher angular values, θ ≳ 4 θ c , the coupling echo coefficient R 12 (= R 21) at the X = 1 level is given as the geometric mean of the direct extraordinary and ordinary reflection coefficients, R 11 and R 22, respectively, R 22 having increased markedly and R 11 showing a corresponding marked decrease. This type of coupling echo is due to a Z-coupling ‘CTR process’. The response to a vertically incident wave linearly polarised in the magnetic meridian and reflected from the X = 1 level is determined numerically, and results agreeing with the observations of Kelso et al. (1951) are obtained, although the propagation mechanism is more complicated than is generally assumed.