Screening can identify individuals at increased risk of or in the early stage of a disease at a time when intervention can reduce the risk of morbidity and mortality. There are many ethical issues that have arisen as a result of screening. These can relate to the process of screening in general or to specific screening programs. Examples of the former include issues related to consent for screening, the utility of the screening tests employed and issues of funding of screening programs and equity of access to screening. Ethical issues related to three specific areas of screening are explored in more detail: reproductive screening, screening for disease with onset in adulthood and newborn screening. It is critical that ethical issues are considered in planning screening programs so as to ensure that the main focus of screening, preventing morbidity, is maximised. There are many lessons to be learnt from the many screening programs that have been conducted worldwide. No doubt new ethical issues will arise as new technologies and new treatments are developed, enabling screening for more conditions at lower relative costs.