The present invention provides an improved process for preparing 5-chloro-2-[(3,4,4-trifluoro-3-buten-1-yl)thio]-thiazole comprising reacting 2-[(3,4,4-trifluoro-3-buten-1-yl)thio]-thiazole with N-chlorosuccinimide (NCS) in the presence of water, the improvement comprising performing the step of reacting the compound of formula (II) with NCS in the presence of a reduced amount of water. The present invention provides an improved process for preparing 5-chloro-2-[(3, 4,4-trifluoro-3-buten-1-yl)thio]-thiazole comprising reacting 2-[(3, 4,4-trifluoro-3-buten-1-yl)thio]-thiazole with N-chlorosuccinimide (NCS) in the presence of water, the improvement comprising performing the step of reacting the compound of formula (II) with an excess molar amount of NCS.