The time effect in a series of flexible and rigid bolaform amphiphiles and their mixed systems with oppositely charged conventional surfactants was investigated. An increase of surface tension with time was found in these systems at surfactant concentrations below the crac. This result can be attributed to large numbers of surfactant molecules being gradually adsorbed on the wall of the vessel, which causes great changes of concentration and composition in mixed surfactant solutions. Contact angle data and UV research supported our proposal. It was also found that this reverse time effect in single bolaform cationic surfactant systems is decided by the structure of the hydrocarbon chains and only happens in flexible cationic bolaform surfactant solutions. (C) 2003 Elsevier Science (USA). All rights reserved.