Abstract: Neostigmine (1 x 10^-7 - 1 x 10^-6 M) and galanthamine (5 x 10^-7 - 6 x 10^-6 M) are determined by measuring their inhibition of acetylcholinesterase immobilized on controlled pore glass. The determination is carried out by a flow injection procedure with spectrophotometric detection. The 3s limits of detection were 0.5 x 10^-7 M neostigmine and 5 x 10^-7 M galanthamine. The relative standard deviations were 1.3% for five determinations of 5 x 10^-7 M neostigmine and 2.0% for six determinations of 2 x 10^-6 M galanthamine. Several reagents for achieving online reactivation of inhibited enzyme were studied. As a result, 2 x 10^-3 M NaF was recommended for reactivation after neostigmine inhibition, and 2 x 10^-4 M substrate solution for reactivation after galanthamine inhibition. The efficiency of the reactivation process was interpreted in terms of the inhibitory mechanisms relating to the above drugs.