The invention describes a process for the isolation of pure
N-vinylpyrrolidone from N-vinylpyrrolidone-containing crude products,
comprising a single-stage or multistage crystallization process, which
comprises passing the mother liquor from the first crystallization stage
either to a distillative and/or extractive purification, or returning it
to an N-vinylpyrrolidone-containing product stream of the preparation
process.
