Sixteen wildebeest were marked with radio transmitters and tracked for varying lengths of time during the period between late November, 1971, and mid-July 1972. They were repeatedly radiofixed from an aircraft prior to, during and after their annual wet season visit to the Serengeti Plain. Fix-to-fix tracks of animals showed that each hurried to the Plain at the onset of the rains, performed oscillatory movements over an individually distinct, elliptically shaped, fractional part of the Plain area, and departed into the woodland as the Plain dried out. Average fix-to-fix rate of travel approximated 3–75 km/day. Large aggregations of animals, armies, were smaller and more restless in the woodlands than on the Plain. Smaller aggregations included within armies, troops, varied in size as a function of activity. They were small when feeding and large when marching. Troops averaged larger in the woodlands mostly because they were more often marching there than on the plain. The tracked animals were equally successful in finding green forage in the presence of water in both habitats. The item in shortest supply appeared to be the presence of green forage in the woodlands and of water on the Plain. It is concluded that structural attributes of the woodlands, by lowering the security level of animals, played a part in making the Serengeti Plain attractive to the animals.