Transcription factors (TFs) bind to the regulatory regions of genes in a cooperative manner. This article describes a method to detect pairs of transcription factor binding sites which co-occur in known regulatory regions more often than expected by mere combination of the individual binding sites. We determine frequently co-occurring TF pairs and evaluate the method using known TF interactions. Furthermore we use co-occurrence scores to assess the regulatory potential of a sequence region by calculating a graph-based score. We show results for the score on known regulatory regions.