'I.S.' is a series of peach x almond clones, selected by the DCDSL "G. Scaramuzzi" of the University of Pisa, differentiated from 'GF 677' by the different degree of scion induced vigour. 'Castore' and 'Polluce' represent two of the most promising clones of the 'I.S.' series. 'Castore', selected as I.S.5/19, gives satisfactory results by in vitro propagation. It prefers fertile and permeable soils, whereas it is unsuitable for clay and waterlogged soils. The induced vigour (about 30% lower than 'GF 677') allows good growth control. Production, yield efficiency, fruit quality are also very good. Moreover, this stock adapts to poor soil where it shows good growth and yield efficiency similar to 'GF 677'. 'Castore' showed a resistance to calcareous soil slightly lower than 'GF 677'. 'Polluce', selected as I.S.5/8, is similar to 'Castore' for proliferation and rooting results by in vitro propagation. Like other peach x almond hybrids it is not suitable for wet, clay and poor drained soils, while it adapts to permeable soils, with medium or high fertility and medium-high lime content. It induces about 20% lower vigour than 'GF 677', and is associated with good production and high yield efficiency as well as good fruit characteristics. It reaches earlier vegetative balance than 'GF 677', and shows good productivity, yield efficiency and better fruit quality. These stocks could become alternatives to 'GF 677' especially in high ('Castore') and medium-high ('Polluce') fertile soils.