Semi theoretical models have been proposed to account for the mechanism of membrane oscillations involving, electrokinetic phenomena in systems where (i) concentration difference DeltaC is finite and DeltaP is varying but the current is fixed, and (ii) DeltaC = 0, pressure difference DeltaP is fixed across the membrane and imposed current is fixed. The formalism leads to the van der Pol equation in both cases. Computer simulation has also been attempted, which indicates oscillations in the former case. (C) 2003 Elsevier Science (USA). All rights reserved.