On 17-22 April 1993, a workshop took place in the framework of the European Commission's measurement and testing (BCR) programme on the state of the art in the determination of polychlorinated dibenzo dioxins and furans. Discussion focused on dibenzo furans ("dioxins") in fly ash (emission from incinerators) and food products (milk contamination). A special issue of "Fresenius' Journal of Analytical Chemistry" (vol. 348, No. 1-2, 1994. Guest editors: E.A. Maier, B. Griepink and G.U. Fortunati) contains 27 contributions from top European specialists who participated in BCR projects in this field, plus a paper summarizing the round table discussions which took place at the meeting.