Gamma-ray variability of the BL Lacertae object markarian 421

We report on the gamma-ray variability of Mrk 421 at E(gamma) > 300 GeV during the 1995 season, and concentrate on the results of an intense multiwavelength observing campaign in the period April 20 to May 5, which included > 100 MeV gamma-ray, X-ray, extreme-ultraviolet, optical, and radio observations, some of which show evidence for correlated behavior. Rapid variations in the TeV gamma-ray light curve with doubling and decay times of less than or similar to 1 day require a compact emission region and significant Doppler boosting. The TeV data reveal that the gamma-ray emission is best characterized by a succession of rapid flares with a relatively low baseline level of steady emission.