The extensive use of trees in urban environments is a common feature of many cities of the temperate mid-latitude arid zones of western Argentina. Although beneficial in summer, trees can reduce solar access in urban buildings to an important extent. Permeability to solar radiation of the crowns of the most commonly used deciduous trees in the city of Mendoza was measured throughout their yearly foliation cycle. Results of permeabilities of four species of trees to global, diffuse and direct radiation are presented, for different zones, of their canopies and at typical stages of their annual cycle. Discussion of results and proposals for future research are also included.