Chlorosubstituted derivatives of tacrine (l), 1,4-methylenetacrine (2), and their in vitro acetylcholinesterase (AChE) and butyrylcholinesterase (BChE) inhibitory activities are described. The most potent analogues are 6-chlorotacrine (1 b) in AChE and 7-chlorotacrine (lc) in BChE inhibition.