This paper highlights some of the development initiatives in microwave magnetrons stimulated by materials and techniques breakthroughs of the past decade. The paper concentrates on the performance achievements and prospects for miniature, rugged magnetrons, designed for rapid switch on with highly refined operational parameters such as rapid r.f. build-up, low jitter, and high frequency and/or pulse stability. Recent development trends towards higher and higher mean to peak power ratios are discussed, along with phase locking for high coherence and frequency control. The traditional image of the magnetron as a simple fixed frequency pulse transmitter for low duty ratio applications gives scant recognition to the diversity of designs and range of performance of modern magnetrons. The magnetron remains one of the most widely used microwave power sources, employed in some of the most sophisticated military systems, especially those that are airborne or otherwise environmentally punishing. Consistent characteristics of magnetrons are high efficiency, small size and weight, and ease of manufacture. Furthermore, the relatively low operating voltage of magnetrons means that power supplies and modulators can be designed with the minimum of complexity, and packaged within tight volume constraints.