The aim of this research was to observe histological developments during the early stages of graft formation between some spur apple varieties and apple rootstocks in order to assess compatibility/incompatibility related to different growing rate of the plants used. As rootstocks, one year-old clonally propagated A2, B118, M111 (vigorous) and M7, MI6, Pj80 (semi-dwarfing) were used. Scions were taken from one-year-old shoots of Scarlet Spur, Red Spur and Redchief spur apple varieties. Rootstocks were planted in the field in winter 2007 and whip-grafted in April 2008. An evident incompatibility was not observed in the combinations. Sufficient callus proliferation was visible in all the combinations. Successful cambial and vascular connection was apparent in the 90-day sections. In the 120(th) and following sections, it was observed that callus usually filled all the gaps between the rootstock and the scion. Xylem and phloem strands successively bridged the union. However, especially Pj80/Redchief and M16/Red Spur should be followed up in subsequent years in the field conditions because of the excessive callus formation between the stock and the scion.