Global gene expression profiling of bacteriophage BFK20 infecting the industrial L-lysine producer Brevibacterium flavum CCM 251 was performed using DNA microarray. The relative gene expressions were measured in fourteen time samples collected during phage development. Phage genes were classified as early, middle, late or unassigned based on complex expression patterns during infection. Temporal classification of BFK20 genes was in concordance with previous predictions. However, proposed late regulatory genes were reclassified and new functional assignments for ORF55 were strongly suggested. Furthermore, we consider possible functions of other genes and their products regarding coexpression pattern by using "guilt-by-association" algorithm. Microarray results were validated using real-time RT-PCR. The detailed description of phage BFK20 transcriptional profile can answer the basic questions of its life cycle and it also can help to prevent phage contamination during industrial fermentation. In addition, this work presents the first complete microarray time course study of gene expression utilizing loop design.