Compounds of the formula inhibit the activity of endothelin. The symbols are defined as follows: R1, R2 and R3 are each independently (a) hydrogen, except that R1 is other than hydrogen; (b) alkyl, alkenyl, alkynyl, alkoxy, cycloalkyl, cycloalkylalkyl, cycloalkenyl, cycloalkenylalkyl, aryl, aryloxy, aralkyl or aralkoxy, any of which may be substituted with Z1, Z2 and Z3; (c) halo; (d) hydroxyl; (e) cyano; (f) nitro; (g) —C(O)H or —C(O)R6; (h) —CO2H or —CO2R6; (i) —SH, —S(O)nR6, —S(O)m—OH, —S(O)m—OR6, —O—S(O)m—R6, —O—S(O)mOH or —O—S(O)m—OR6; (j) —Z4—NR7R8; or (k) —Z4—N(R11)—Z5—NR9R10; and the remaining symbols are as defined in the specification.