Progress is outlined in the design of c.w. and pulsed lasers, using methyl cyanide, dimethylamine and a mixture of methane and nitrogen, for use at wavelengths in the 337 μm region. Output stability is stated to be a function of cathode material, gas type and pressure and discharge current for any given laser design. Brass appears to be the best cathode material. With input power at 1 kW, outputs of 7 mW (c.w. laser) and 1 W (pulsed laser) were obtained, the gas used making no significant difference to these figures. An optimum working pressure of 0.55 torr was established using a mixture of 60% methane and 40% nitrogen. Tube life with all three gases is typically 100 hours. Initial investigations into transmission properties of various materials at sub-millimetric wavelengths show that p.t.f.e. and t.p.x. (polyolefin thermoplastic) make the best lenses and windows, and that black polythene makes the best attenuator. Investigations into atmospheric absorption at this wavelength indicate that, dependent on temperature and relative humidity, attenuations of between 36 dB/km and 204 dB/km can be expected.