The development of new sensors for landmine detection is an active area of research. Microwave radiometry is a field of remote sensing concerned with the measurement of thermally emitted radiation in the microwave band. This paper describes the design, testing and performance of an experimental microwave radiometric measurement system for use in landmine detection. The aim of our research is to set up an experiment to assess the potential of microwave radiometry for landmine detection and also to establish the relative merits of various frequency bands. We have designed and constructed a sensitive radiometric receiver consisting of a switchable front end (i.e., 10 GHz, 35 GHz or 90 GHz), followed by an IF amplifier chain of bandwidth 1 GHz, and power detector. The radiometer design, hardware and performance are described.