5-Chloro-1,5-dihydro-2H-pyrrol-2-ones are easily alkylated at the 5-position by organomagnesium or organozinc compounds and diethyl sodiomalonate leading to corresponding 5-alkyl-1,5-dihydro-2H-pyrrol-2-ones in high yields.Key words: organometallic compounds, alkylation, 1,5-dihydro-2H-pyrrol-2-one.