A high definition colour television transmission system in which wide band luminance information (Y, Figure 1) is utilised to produce a first luminance information portion comprising lower frequency (0 to 3.8 MHz) and middle frequency (3.8 to 5.5 MHz) components and a second luminance information portion comprising the middle frequency (3.8 to 5.5 MHz) and upper frequency (5.5 to 8.8 MHz) components. The first luminance information portion (Y1, Figure 2) is transmitted by way of a first transmission path together with a colour subcarrier (f sc ) modulated by colour information. The bandwidth of the colour information is such that the modulation components lie substantially within the bandwidth of the middle frequency components. The second luminance information portion is frequency shifted to lie within 0 and 5 MHz (Y2, Figure 3) and is transmitted by way of a second transmission path. The two transmissions may also carry sound signals (f s1 , Figure 1, f s2 , Figure 3). The two transmissions may be jointly received for the provision of a high definition display but the invention has the distinct advantage that the signal of te first transmission path may be received alone by currently manufactured television receivers for reproduction of a display of a quality which is accepted as normal.