A discussion of means of sharing the radio frequency spectrum above 3400 MHz among terrestrial microwave relay, satellite relay, and satellite earth stations for fixed or mobile communication services, including direct broadcast from satellites. Each of nine generic direct interference modes and a number of scatter modes adds to the interference constraint. An illustrative compatible configuration that goes beyond present technology but seems feasible is outlined. Private radio services, as well as carrier services, should be considered. Tight coordination and cooperation are essential. Licenses for spectrum allocations should go to the highest bidder each year to ensure intensive use. Array-lens antennas should be used for high gain on board satellites, adaptive arrays for fixed earth terminals, and automatic direction-following arrays for all uses of satellite relays. 12 pp.