The mechanisms by which plants restrict the growth of pathogens include transient activation of numerous defense‐related genes. Box P is a putative cis‐acting element of a distinct group of such genes, including those encoding the enzyme phenylalanine ammonia‐lyase (PAL). A DNA‐binding activity to Box P was identified in nuclear extracts from cultured parsley cells and a cDNA encoding the protein BPF‐1 (Box P‐binding Factor) partially characterized. BPF‐1 binds to this element with specificity similar to that of the binding activity in nuclear extracts. BPF‐1 mRNA accumulates rapidly in elicitor‐treated parsley cells and around fungal infection sites on parsley leaves. This accumulation is, at least partly, due to a rapid and transient increase in the transcription rate of BPF‐1. Moreover, tight correlation between the relative amounts of BPF‐1 and PAL mRNAs was observed in different organs of a parsley plant. These results are consistent with the hypothesis that BPF‐1 is involved in disease resistance by modulating plant defense gene expression.