I will present some results for modeling of leukemia and HIV, and the resulting treatment implications. The mathematical models consist of ODEs, determined in consultation with medical researchers. In silico experiments and simulations provide evidence to help in making treatment recommendations. Control theory allows treatment goals to be incorporated into treatment recommendations, while taking into account issues such as severity of drug side effects. Although the focus of my talk will be on the mathematics being applied, I will also include some relevant information about the diseases being modeled.