Electrical membrane fluctuations are treated as due to sequences of ion pulses passing through the membrane. A mathematical procedure is developed which permits calculation of the power spectra for sequences in which the pulses can have Poisson or non-Poisson interval distributions and may or may not have coupled pulse parameters. It is shown that there probably exist specific sequences which are intimately related to membrane 1/f and burst noise. In particular, emphasis is placed upon sequences with non-Poisson interval distributions and (...) their implications for membrane structure. A variety of experiments is suggested which will help to distinguish among the alternatives presented. (shrink)