Traditionally pharmacokinetic studies have been performed in small homogenous groups of subjects, often normal healthy, young male volunteers. These studies are well controlled and generate meaningful baseline data. However, concern has been expressed that insufficient data is collected at an early state in the target population during a drug's development. Logistically studies during Phase III are difficult, control is lacking and what data that is generated is very sparse. In recent years there has been a growing interest in techniques capable of analyzing sparse data and there is now pressure on manufacturers to obtain more kinetic and dynamic information from Phase III studies. The issues, problems and the current status of population based studies will be discussed.