A series of quantum-cascade lasers emitting at lambda approximate to 11 mu m with different numbers of cascades in the active region - between 25 and 200 -grown by gas-source molecular beam epitaxy, is compared in terms of their room-temperature performance in pulsed mode as a function of the number of cascades. Within the given range of cascade number we observe a superlinear increase in both slope efficiency and differential quantum efficiency as functions of cascade number. The differential quantum efficiency scaled per number of cascades, however, shows a sublinear increase. A differential quantum efficiency of 17% per cascade and pulse power exceeding 7 W per facet, both at room temperature, was demonstrated for quantum-cascade lasers with 200 cascades. All lasers with stripe width below 30 mu m are operated in the fundamental TEM(00) spatial mode. This combination of high pulse power and TEM(00) mode operation for room-temperature mid-infrared laser emission can be attractive for a number of applications. (C) 2010 Elsevier B.V. All rights reserved.