The vegetative growth and graft compatibility were evaluated in different pear cultivars ('Conferencia', 'Williams', 'Decana de Comice' and 'Mantecosa Hardy') with different degree of compatibility grated on two rootstocks (quince 'BA-29' and pear 'OHF-87'). The study was carried out over 2 years in a field at CITA de Aragón in Zaragoza. The following growth parameters were measured: graft length, number of branches, length between nodes, and trunk diameter at the three graft zones: above, below and at the graft union. The internal characterization of the different unions was also recorded with the aim of elucidating whether the growth parameters were related to the degree of graft compatibility. The rootstock 'OHF-87' showed a good graft compatibility with all the tested cultivars. The cultivar 'William' grafted on the rootstock 'BA-29' exhibited much slower growth and thickening of the trunk diameter at the graft interface, and therefore it was classified as an incompatible combination. The internal structure, thickening at the graft interface and the graft length were found to be related to graft compatibility.