A new regular polyampholyte, namely poly(N,N-diallyl-N-octadecylamine-alt-(maleic acid)), was studied as an additive to crude oil. The amphiphilic polyampholyte proved to be an efficient pour point depressant, to inhibit the deposition of wax, and to improve the viscosity of waxy crude oil from the Akshabulak oilfield (Western Kazakhstan). On optimizing the concentration of the polymer, both the kinematical viscosity and the pour point of waxy crude oils were found to be strongly decreased. The morphology of the paraffin aggregates formed was compared before and after heat treatment of the waxy crude oils, in the presence and the absence of the polymer. The rheological characteristics of the waxy crude oil were markedly improved, in particular, by decreasing the plastic viscosity and the yield stress values upon addition the polymer. The inhibition of wax deposits in the presence of the amphiphilic polyampholyte was interpreted in terms of its interference with the wax crystallization process because of the formation of inverse micellar structures. Although the interaction of the cationic and the anionic groups on the polymer backbone stabilizes the smaller size of the aggregates, the hydrophobic side chains of the polymer provide nucleation sites and cocrystallize with the paraffins, thus modifying the paraffin crystal structure. (c) 2005 Wiley Periodicals, Inc.