Gamma-ray bursts are among the most energetic explosions in the Universe, and yet their origin has been a mystery since they were discovered in 1973. Early instrumentation showed that the bursts have a huge variety of time profiles and are not associated with any bright or unusual steady sources at other wavelengths. The BATSE instrument on CGRO is more sensitive than any previous GRB detector and is providing a huge (> 2000) and uniform sample. From it we have learned that GRBs are isotropic on the sky and have an intensity distribution that flattens toward fainter bursts. Recently, tremendous progress has been made by measurements performed and enabled by the BeppoSAX mission. X-ray, optical and radio afterglow has been discovered for several bursts. From the accurate positions in these wavelength bands it has been possible to obtain redshifts for 3 bursts and to identify host galaxies for ∼ 10 bursts. From this we now know that most, if not all, GRBs are cosmological in origin with typical distances of∼2&hthinsp;GPc(z≈1).©1999 American Institute of Physics.