An epidemic of 239 human cases of anthrax is reported in the Rukwa Valley area of Tanzania. Although the infecting source was meat from animals dying of the disease, no intestinal cases occurred. Those infected were predominantly males between 15 and 35. The epidemic was seasonal, reaching a peak towards the end of the dry period when cattle were close grazing, and declining rapidly once the rains started and the grass began to grow. The increasing magnitude of annual epidemics suggests that the problem will get worse unless major efforts are made to vaccinate cattle before the epidemic period.