Current speech recognition systems can be categorized into two broad classes; the knowledge-based approach and the stochastic one. In this paper we present a rule-based method for the recognition of Hungarian vowels. A spectrogram model was used as a front-end module and some acoustic features were extracted (e.g. locations, intensities and shapes of local maxima) from spectrograms by using a genetic algorithm method. On the basis of these features we developed a rule set for the recognition of isolated Hungarian vowels. These rules represented by Prolog clauses were refined by the IMPUT Inductive Logic Programming method.