Abstract: The invention relates to novel 5-phenylcarbamoylthiobarbituric acid derivatives of the general formula ##STR1## wherein R.sub.1 and R.sub.2 are each independently C.sub.1 -C.sub.5 alkyl or methoxy,R.sub.3 is unsubstituted phenyl, unsubstituted pyridyl, or phenyl which is substituted by 1 to 3 identical or different members selected from the group consisting of C.sub.1 -C.sub.5 alkyl, C.sub.1 -C.sub.4 cyanoalkyl, halogen, nitro and C.sub.1 -C.sub.5 haloalkyl containing 1 to 5 halogen atoms, or is pyridyl which is substituted by 1 to 3 identical or different members selected from the group consisting of C.sub.1 -C.sub.5 alkyl, halogen, nitro and C.sub.1 -C.sub.5 haloalkyl containing 1 to 5 halogen atoms andR.sub.4 and R.sub.5 are each independently hydrogen, halogen, C.sub.1 -C.sub.5 alkyl, C.sub.1 -C.sub.2 haloalkyl containing 1 to 3 halogen atoms, or are C.sub.1 -C.sub.3 -alkoxy or nitro,and to the tautomers and salts thereof, as anthelmintics.