In recent years, microarrays have become a key experimental tool, enabling the analysis of genome-wide patterns of gene expression. Numerous complex statistical problems arise during the analysis of microarray data and, therefore, only specialized statisticians are able to extract the expressed genes. This tutorial is aimed to help biologists to conduct some, also if rough, analysis of their microarray data immediately afterwards they are produced. After a short review on statistical challenges in microarray studies, complete data analysis, from raw data to differentially expressed genes, was developed using both simulated and real data set. The referring microarray platform was the spotted cDNA microarray and all the computations were developed using the SAS-STAT software.