A review paper was previously published on infrared zoom lenses in the 1980s. Subsequently, a paper was published on infrared zoom lenses in the 1990s. It is timely then to prepare a paper on developments and trends in infrared zoom lenses in the decade since the year 2000. These trends include the shift from scanning systems to charge-coupled device and focal plane arrays, dual-band systems, advances in simulators for target detection, high zoom magnification ratio, off-axis as well as on-axis reflective zoom systems, athermalization, and developments and trends in infrared materials. Examples are presented to illustrate each of these trends. These examples are predominantly mechanically compensated zoom lenses, although one optically compensated zoom lens is also included.