Cohort studies are also known as follow-up or incidence studies. They start with a group of people (cohort) free of the effect (disease or outcome variable of interest). These groups are then classified according to exposure to a potential cause of disease or outcome.

The cohort is followed up to see how new cases of disease (or outcome of interest) are developed between the groups with and without the exposure. Variables of interest are specified and measured for the cohort.

These studies are longitudinal studies, like case-control studies, in that they collect data at different points in time. They are also referred to as prospective studies, referring to the timing of data collection, and not to the relationship between exposure and effect.