The research reported in this paper was necessitated by (a) the great volume of local and international building contracts in the Middle East and (b) the search for the reasons behind the phenomenon of extensive concrete deterioration. Petrological classification, and chemical and x-ray analyses were performed on the aggregates used for concrete production in Kuwait. The results indicated that the coarse aggregates contain no deleterious materials and have no potentially adverse reactions. Thus the aggregates are suitable for good concrete production. Fine aggregates in their unwashed condition are contaminated with clay and contain too much fines, which necessitates careful washing before being used. High-quality concrete made with these aggregates should be expected if efficient washing of the sand is made and if proper mix design and workmanship are provided.