The examination of three dust preparations by two independent laboratories using analytical transmission microscopic techniques has shown that comparable results can be produced. Further interlaboratory collaboration is required, however, to clarify and improve the results that can be obtained. Those areas that require further investigation are data interpretation from energy-dispersive X-ray analysis equipment and counting procedures. The results that have been obtained so far by interlaboratory collaboration are very encouraging, and it is hoped that such joint efforts will be expanded in the future.