1. Maraging steels are characterized by a good combination of strength, plasticity, and ductility, and low notch sensitivity and susceptibility to brittle fracture at low temperatures. Nickel-molybdenum-cobalt steels have the best combination of properties. 2. Maraging steels with a strength of 150 kg/mm2 are best alloyed with 4.0\2-5.0% Mo and 3% Co, which provide the required strength along with adequate plasticity and ductility. 3. The optimal properties of maraging steels are attained by austenitizing at 810\2-830\dgC; a higher austenitizing temperature slightly increases the strength and ductility of the steel with molybdenum and cobalt. The optimal temperature for short aging (3 h) is 450–500°C for the steel with titanium and 500–525°C for the steel with molybdenum and cobalt. 4. Overaging reduces the strength and increases the plasticity and ductility, and also increases the amount of residual austenite. Overaging is more advantageous for the steel with titanium, which acquires approximately the same properties as the steel with molybdenum and cobalt after the optimal heat treatment.