N.sup.2 -naphthalenesulfonyl-L-arginine amides having the formula ##STR34## or the acid addition salts thereof with a pharmaceutically acceptable acid, wherein R.sub.1 and R.sub.2 are members selected from the group consisting of hydrogen and a hydrocarbon selected from the group consisting of C.sub.1-10 alkyl, C.sub.6-10 aryl, C.sub.7-15 aralkyl, C.sub.3-10 cycloalkyl and C.sub.4-15 cycloalkylalkyl, or R.sub.1 and R.sub.2 together form a polymethyleneiminyl group of 3-10 carbon atoms, the methylene groups of which are optionally substituted by one or two alkyl groups of not more than 10 carbon atoms;
- and R' is 1-naphthyl substituted with a member selected from the class consisting of 2-alkylamino, 3-dialkylamino, 4-dialkylamino, 6-dialkylamino, 7-dialkylamino, 8-dialkylamino, respectively, containing not more than 20 carbon atoms, and 5-dialkylamino containing 3-20 carbon atoms;
- or 2-naphthyl substituted with dialkylamino containing not more than 20 carbon atoms.