A systematic study on the use of liposoluble PEG(5000)Bu(3)N(+)Br(-) (1a) as the catalyst in a series of anion-promoted reactions carried out under both liquid-liquid (LL) and solid-liquid (SL) phase-transfer catalysis (PTC) conditions is reported. A comparison of the catalytic efficiency of la and that of popular soluble nonsupported and/or insoluble resin-supported onium salts 1b-i is also included. Classical nucleophilic substitution reactions, i.e., Br-I exchange [reaction (1)] and S(N)2 displacement with a CN-ion [reaction (2)], C-, O-, and N-alkylation reactions [reactions (3)-(9)], formation and reactions of dichlorocarbenes with alkenes [reaction (10)], and sodium borohydride reductions [reaction (11)] were the standard transformations examined. The results show that la behaves as an efficient easily recyclable phase-transfer (PT) agent under both LL- and SL-PTC conditions, with its catalytic activity being generally superior to that of insoluble resin-supported PT agents 1b,d and favorably comparable to that of popular soluble nonsupported onium salts 1c,e-i.