Since the first reports of tobacco transformation experiments in 1983, a number of fundamental processes, such as gene expression, cell metabolism, or plant development, are being studied using gene transfer experiments. The spectrum of plant species amenable to transformation is continuously widening. This is partly because of the refinement of tissue culture techniques and also because of the development of more and more diverse tools for gene transfer and expression. In this chapter, I will give a list of plasmid constructs containing various components useful for expressing foreign genes in plants: expression cassettes into which genes of interest can easily be inserted, assayable reporter genes that allow accurate quantification of gene expression, selectable marker genes for the selection of transformants, and plant promoters to achieve more specific patterns of gene expression.