General Linear Model (GLM) is a statistical method that can be applied to analyze data generated from different fields of medical research. However, accordingly to our consulting experience, bio-medical researchers do not possess adequate understanding of the technique. Therefore, we present a hypothetical data set similar to those generated by intervention studies to illustrate the use of GLM for various analyses such as repeated measures of analysis of variance. We also examine the usefulness of GLM when there are missing observations in the data set, a problem widely encountered in follow-up studies. Throughout the article, we demonstrate the procedures required to run GLM using the commonly available statistical software package, SPSS, and explain how the outputs should be interpreted. Readers will be equipped with the basic skills to analyze their own research data using GLM after reading this manuscript.