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Measurements made by the DMR experiment on COBE give evidence for anisotropy of the cosmic microwave background on angular scales from a quadrupole to 10 degrees. These observations give information about primordial gravitational potential fluctuations. A number of ground-based and balloon measurements are exploring smaller angular scales which provide constraints on scenarios for the formation of structure in the observable universe. Some of these experiments provide useful upper limits and others see signals which may well be cosmic background anisotropy. A review will be given of the experimental situations with special reference to the results of the millimeter wave anisotropy experiment (MAX).