This study aimed to define a method for surveying the naturalisation processes occurring in adult plantations stands of Aleppo Pine. In stands planted in the South-Eastern Salento peninsula (Southern Italy) during the 1950s, 23 study plots were identified, each with a different level of naturalisation. A survey was performed in these plots on the demographic and biometrical parameters commonly used in silvicultural studies, not only for the tree populations but also for the shrubs. The results indicate that, of all the parameters considered, it is the Hart-Becking Spacing Index which seems to best represent the processes being surveyed. It can therefore also be used to determine the appropriate intensity of thinning in order to encourage the development of such naturalisation processes.