The technique of marking, is considered a scientific technique that is generally used in the ecological field to estimate both the main characteristics and certain population size. This method of marking, are used when the researcher cannot stop to particularly study each individual who composed the population, so that comparing certain samples taken at different times. With this marking technique, the first step is to mark a number of individuals, which are studied and are then released. Later, the same individuals recapture is and examines the relationship between the recaptured with respect to the total number of captured. In this way, is achieved estimate of population size. In the area of epidemiology, marking technique is used to estimate the progression from the registration of certain diseases, or from certain conditions.

I.e., seeks to the estimation of the number of individuals needing specific service at one point. For example, application of this method may be to estimate the number of children with learning problems, or, in more severe conditions like for example, people infected by HIV, or with some type of drug addiction. A. Verastegui hold.