This paper traces the development of the Maternal Teaching Style Instrument (MTSI) at the Demonstration and Research Center for Early Education (DARCEE). The MTSI was developed to document changes in maternal behavior; to better understand the role of maternal behavior as it influences children's cognitive growth and development and to redefine DARCEE's approach to training mothers by delineating those aspects of maternal behavior which appear to enhance the development of children's cognitive skills. A number of studies using the MTSI are reported along with validity and reliability testing of the instrument. Research results indicate a number of implications for mothers of preschoolers and those who train them. Included in this report is background information on DARCEE's early education program for low income children, the research program, and studies conducted on mother-child interactions. Appendices include directions for administration and coding of the MTSI, the scoring grid, and materials for the MTSI. (MS)