A detailed description of an automatic low‐temperature apparatus to be used in single‐crystal diffractometry is given. The crystal is cooled by a stream of nitrogen gas. Prevention of ice formation on the crystal is achieved by heating the outer parts of the gas stream by a conical metal device. The unit‐cell dimensions of α‐quartz have been determined in the temperature range 86–298 K with this apparatus on a four‐circle diffractometer