1-Aryl-2-acylamino-ethane compounds of formula (I), wherein R1 is aryl or heteroaryl; R2 is hydrogen, lower alkyl or aryl-lower alkyl; R3 is hydrogen, lower alkyl, aryl or heteroaryl; R4 is aryl or heteroaryl; X is C1-C7alkylene, C2-C7 alkenyline or C4-C7 alkanedienylene, and Am is an unsubstituted or mono- or di-substituted amino group, a disubstituted amino group being understood as including also an amino group in which the amino nitrogen is bonded into a ring, or a salt thereof, have valuable pharmaceutical properties and are especially effective as NK1 antagonists. They are prepared in a manner known per se.