Folding and aggregation mechanisms are in common to most proteins. Proteins differ whether they are folded or intrinsically unfolded/disordered, however, all aggregate over partially unfolded intermediates and the mechanism in most cases conforms to nucleation and growth. In order to get to know more of the mechanism, we studied folding and aggregation to amyloid fibrils of two homologous proteins, stefins A and B and their chimeric variants. Further, we performed cellular studies of certain EPM1 stefin B mutants. Part of our studies was devoted to the possible common mechanism of how amyloid proteins form pores within membranes. Thus far we checked model membranes and it was shown that oligomers and protofibrils of stefin B release calcein from lipid vesicles, increase pressure on the lipid surface, and finally lead to step-wise currents. The capacity of the oligomers to bind to cellular membranes correlates with an increase of reactive oxygen species (ROS) and leads ultimately to cell death. We will present novel studies supporting the “amyloid pore” hypothesis, which assumes that the oligomers of amyloidogenic proteins behave similarly to pore forming peptides. The oligomers likely bind various cellular membranes and even perforate them. With modern high–resolution microscopic methods it should be possible to image these oligomers (of the size between 20 and 200 nm) and in such a way determine their detailed localization and down-stream processes.