Engineered semiconductor quantum structures that enforce carrier confinement in all three spatial dimensions have recently become of interest for potential applications in the sensing of infrared radiation via intersub-level transitions. These structures, most often called quantum dots, may offer a viable alternative to the mercury cadmium telluride semiconductor and GaAs/(Al,Ga)As quantum-well structures for infrared detection. Their major advantages for detection include (i) operation under normal-incidence illumination, (ii) a predicted high responsivity due to a long electron lifetime in the excited states, and (iii) a potential for high-temperature operation. This paper will review the current-state-of-development of (In,Ga)As/GaAs quantum-dot infrared detectors that are sensitive to light in the middle wavelength infrared (3-5 μm) region of the electromagnetic spectrum. The paper will also discuss some of the leading edge experimental results that suggest that quantum-dot active regions may offer a route to elevated device operating temperatures (> 150 K).