The performance of a single-mode single-frequency CO2laser operating on a single rotational-vibrational transition is described. The laser is sealed off with a length of 152 cm, and it has a continuous output power of 60 watts. Mode-competition phenomena are of great importance in obtaining this high output power of high spectral purity. In-order to maintain the high output power over a long period of time, we constructed our laser with a water vapor replenisher and a bypass to reduce gas segregation in the discharge. The use of a plane parallel germanium out-coupling window creates conditions for a single rotational-vibrational transition. The experimental procedure and results are discussed.