Abstract: A method for declaring the presence of ventricular fibrillation from an incoming electrocardiograph signal includes sampling the signal at a first frequency and filtering the same to produce a secondary frequency lower than the first frequency. This filtered signal is passed to a linear predictor which fits a model signal spectrum to the actual signal spectrum and computes coefficients representative of bandwith and mean frequency of the signal over a short time interval. The method then includes comparing the coefficient of bandwith with a preselected threshold value to determine whether it exceeds same, and, if so, comparing the coefficient of mean frequency with a range of values to determine whether it falls within that range whereby ventricular fibrillation is then declared to be present.An apparatus to carry out the method substantially as described above, is included in this invention.