To understand the links between CFTR mutations and the development of cystic fibrosis (CF) phenotypes, it is imperative to study the transcriptome in affected cell types. Microarray expression profiling provides a platform to study global gene expression in detail. This approach may provide the necessary information to segregate phenotypic characteristics of CF, differentiate between genetic or environmental factors, and assess the advent and progression of disease phenotypes. Moreover, if a "CF signature" of genes with altered expression is defined, this can be used to monitor effectiveness of treatment. We provide here detailed protocols and tips for collecting and preserving tissues and cells, and preparing total RNA. We also outline novel strategies for experimental design and data analysis, and describe some powerful gene and pathway discovery tools.