Published online by Cambridge University Press: 30 March 2016
Recent precise observations of the cosmic microwave background (CMB) isotopy and experiments in progress are summarized. The current measurements on all angular scales are approaching sensitivities of the order of ΔT/T ≈ 10-5. Nearly all experiments are observing positive detections. Most assume the detection to be due to galactic emission or other foregrounds or systematics and not due to primordial anisotropies in the CMB. The context and significance of these observations are discussed.