Heterobiaryl derivatives of the formulaR.sub.1 NH--X.sub.1 --X.sub.2 --X.sub.3 --Y.sub.1 --Y.sub.2 --Y.sub.3 --Y.sub.4 --E (I)whereinR.sub.1, X.sub.1 to X.sub.3 and Y.sub.1 to Y.sub.4 are as defined herein, the tautomers, stereoisomers and mixtures thereof, and the salts, particularly the physiologically acceptable salts, thereof with organic or inorganic acids or bases. The derivatives have valuable pharmacological properties, such as inhibiting cell-cell aggregation and cell-matrix interactions.