This paper reports a theoretical and experimental investigation of a microwave magnetically tunable band-pass filter. Based upon this work a filter, tunable over more than 1200 MHz at x band with a bandwidth in the range from 230 to 17 MHz having an insertion loss as low as 1 dB can be obtained. The filter is remarkably free of spurious responses and has a rejection band of over 2 G (Hz) whose attenuation is more than 25 dB. The theoretical study has led to formulas giving center frequency, bandwidth, and insertion loss as functions of filter geometry. The filter has important application for electronic tuning in microwave circuits being particularly suitable as an electronically tunable preselector.