The geotechnical behaviour of volcanic materials has some particularities and differences with respect to non volcanic materials that makes it a subject still under investigation. These differences increase for those volcanic materials that share typical properties of both soils and rocks. This is the case of low density pyroclasts, referred in this paper. The results obtained from an extensive testing programme carried out on pyroclasts samples from different places of the Canary Islands are presented. Some practical correlations between strength and other properties are also included.