Preparation of two new Polish candidate reference materials is described. The consecutive steps involved collection of appropriately large quantities of Tea Leaves (INCT-TL-1) and Mixed Polish Herbs (INCT-MPH-2) respectively, comminution, sieving, homogenization, preliminary homogeneity testing, distribution into containers, final homogeneity testing, and radiation sterilization followed by microbiological investigation. Methods of determination of moisture content were established and various approaches to the determination of particle size distribution were investigated. Worldwide interlaboratory comparison was organized in which 109 laboratories from 19 countries participated. Laboratory averages from all participants (over 1400 results for each of the materials for over 70 elements) are presented. The method of data evaluation is briefly outlined and preliminary strategy of certification which will be the subject of final report(s) published at a later date is announced.