2-oxyindole derivatives represented by the following general formula: ##STR1## where R.sub.1 is selected from the group consisting of hydrogen, C.sub.1-4 alkyl, C.sub.2-4 alkenyl, benzyl and phenethyl; A is --CH.dbd.CH-- or ##STR2## wherein R.sub.2 or R.sub.3 may be the same or different and are selected from the group consisting of hydrogen and C.sub.1-4 alkyl; R.sub.6 and R.sub.7 may be the same or different and are selected from the group consisting of hydrogen, C.sub.1-4 alkyl, benzyl, phenethyl and together with the nitrogen atom, a heterocyclic group selected from the group consisting of a piperidino, morpholino, piperazino or thiazolino group; and m and n each are zero or a positive integer with m+n being no more than 11. The 2-oxyindole derivatives have excellent effects on the inhibition of platelet aggregation.