The dichotomy of topic and focus, based, in the Praguean Functional Generative Description, on the scale of communicative dynamism, is relevant not only for a possible placement of the sentence in a context, but also for its semantic interpretation. An automatic identification of topic and focus may use the input information on word order, on the systemic ordering of kinds of complementations (reflected by the underlying order of the items included in the focus), on definiteness, and on lexical semantic properties of words. An algorithm for the analysis of English sentences has been implemented and is discussed and illustrated on several examples.