Density measurements of dodecyl- (C(12)DBACl), tetradecyl- (C(14)DBAC1), hexadecyldimethylbenzylammonium chloride (C(16)DBACl) and of decyl- (C(10)DBABr) and dodecyldimethylbenzylammonium bromide (C(12)DBABr) in aqueous solutions at T = 15degreesC and T = 25degreesC have been carried out. From these results, apparent and partial molar volumes were calculated. Positive deviations from the Debye-Huckel limiting law provide evidence for limited association at concentrations below the critical micelle concentration. The change of the apparent molar volume upon micellization was calculated. The relevant parameters have been presented in function of the alkyl chain length. Apparent molar volumes of the present compounds in the micellar phase, V-phi(m) and the change upon micellization, DeltaV(phi)(m), have been discussed in terms of temperature and type of counterion. (C) 2003 Elsevier Ltd. All rights reserved.