There is provided, novel, transient pro-drug forms of L-DOPA (3,4-dihydroxy-L-phenylalanine), having the formula: ##STR1## wherein R represents a hydrogen atom, an acyl group, a ##STR2## group, a --CO-pyridyl group, and a --CO--R.sub.3 group, wherein R.sub.3 represents the residue of any N,N-C.sub.1 -C.sub.2 dialkylamino acid or a C.sub.4 -C.sub.6 cycloalkylamino acid ##STR3## wherein R.sub.1 represents a member selected from the group consisting of a hydroxyl group and a --OM group, wherein M is an alkali metal (Na, K, etc.) or an ammonium ion; and wherein R.sub.2 represents a member selected from the group consisting of a ##STR4## group, a --CO-pyridyl group, and a --CO--R.sub.3 group, wherein R.sub.3 represents the residue of any N,N-(C.sub.1 -C.sub.2)-dialkylamino acid or a C.sub.4 -C.sub.6 -cycloalkylamino acid ##STR5## wherein R represents an acyl group; wherein R.sub.2 represents a hydrogen atom; and wherein R.sub.1 represents a --NHCH(R.sub.4)COOR.sub.5 group, wherein R.sub.4 represents the residue of any naturally occurring amino acid, and wherein R.sub.5 represents a member selected from the group consisting of a hydrogen atom, a C.sub.1 -C.sub.5 alkyl group (e.g., methyl, ethyl, propyl, butyl, pentyl), and a C.sub.1 -C.sub.5 alkylaryl group (e.g., --CH.sub.2 --C.sub.6 H.sub.5, --CH.sub.2 --CH.sub.2 --C.sub.6 H.sub.5, etc.), and the HX salts thereof, wherein X is a conventional pharmaceutically acceptable acid addition salt anion (e.g. chloride, bromide, perchlorate, methanesulfonate, succinate, etc.).These compounds are all useful in the treatment of Parkinson's Disease.