In material science and technology, computerized systems have been created with information on many types of materials and properties. Many properties, such as mechanical properties, are strongly related to the chemical composition, heat treatment history, and microstructure. Unfortunately, microstructural parameters are represented to a very limited extent in existing databases and then restricted only to a few parameters such as the phase fraction or average grain size. For detailed analysis of property data, this is a serious drawback. Without detailed information about the microstructure, a more complete understanding of properties can never be developed. The aim of the present work is to introduce a representation of microstructures both in qualitative and quantitative form suitable for a material property database. A system with microstructural description and microstructural images of various engineering materials and their treatment data has been developed. Materials in the database are welded simulated stainless steels, sintered high-strength steels, ferritic-pearlitic steels, aluminum-alloybased composite, induction-hardened microalloyed steel, and deformation-dilatometry-tested microalloyed steel. The database covers materials specification, metallographic characteristics, and microstructural images. Later, property data will be added. Both qualitative morphology descriptions of microstructure and the definitions of quantitative parameters are included. Modern automatic image analysis of original structures as well as of database-collected images was used to characterize microstructures. Contents, sizes, and shapes of grains, particles, inclusions, voids, packages, bands, agglomerates, and phases were measured. Examples of database applications are given.