Ancient mortars are valuable evidence of old masonry techniques. There are two kinds of specialists interested in this type of evidence: technologists and archaeologists. Their different requirements call for different analytical procedures. Relevant problems are discussed in the paper. Special attention is given to the author's procedure of comparative analysis, a system specially adapted to archaeological needs. Its main objective is to classify samples according to their original recipes which serve as calling cards for particular groups of masons. The need for standardized procedures which will enable comparison of results from different laboratories is also stressed. See also AATA 19-1792.