The use of an electron microprobe as a research tool will be considered. The theory of operation of this instrument will be briefly discussed. The different possible modes of data presentation will be given. These will include graphical representation on a recorder, video representation of scanned area using backscattered electrons, absorbed electrons, and X-rays, and the accumulation of quantitative data on scalers. Qualitative, semiquantitative, and quantitative analysis will be included in the discussion. Also included will be the importance of specimen preparation in microprobe analysis, and a number of different examples for various types of specimens will be given. These will include such materials as metals, glasses, ceramics, and semiconductors. Consideration will be given to the analysis of thin films as well as bulk materials. Some of the problems encountered in the analysis of thin films will be discussed as well as ways of circumventing these problems. Examples will be given to illustrate the type of problems and the means of approach in cases where qualitative analysis, semiquantitative analysis, and quantitative analysis are desired. In the latter case, the different types of corrective procedures which can be used will be discussed. These include correction for absorption, fluorescence, and atomic number.