The essential difference between ice stream and inland ice and the cause of ice streaming are not known. In order to study these problems, velocities have been measured on and near ice streams B and C by repeated tracking of TRANSIT satellites. The results confirm the difference in mode of flow between fast on ice stream B and slow on the interstream ice ridges. Also as expected, ice stream C is nearly stagnant, which with other evidence of formely fast flow confirms its recent slowing and current thickening. The drainage of ice stream B has a neagative balance equivalent to thinning by 0.15¿0.05 m yr-1 over the entire catchment. The lower portion of the ice stream is thickening at about 2 m yr-1, but the overall behavior is thinning. This general thinning is probably partly due to progressive extension of the ice stream into inland ice. The transition from inland ice to ice stream seems to occur irregularly both spatially and in time, with rafts of inland ice being carried into the ice stream and slowly incorporated. ¿ American Geophysical Union 1987