Conditions for the establishment of in vitro cultures of Marianna 2624 and Pixy plum rootstocks of certified sanitary status (free from Prunus ringspot, prune dwarf and plum linepattern ilavirus, Phytoplasmae and Xylella fastidiosa) were determined. Buds were generated in 100% of the shoot apices of Marianna 2624 implanted in Murashige-Skoog medium pH 5.7 containing 30 g/l sucrose and 5 g/l agar (Basal medium: MB), and supplemented with 1.5 mg/l benzylaminopurine (BAP) and 1.0 mg/l indolebutyric acid (IBA). Shoots differentiated and elongated in the same medium. The rate of propagation was 1.6 shoots/explant every 45 days, from the third culture cycle on. An average 4 roots per explant developed every 4 weeks on all 3-4 cm long shoots cultured on BM + 1 mg/l BAP + 0.5 mg/l IBA. Buds generated in 70% of Pixy shoot apices implanted in BM + 1.0 mg/l BAP and 0.5 mg/l IBA. From the third subculture on, each explant generated an average of 5 buds every 4 weeks. Vigorous shoots, 3-4 cm long, resulted every 4 weeks from the culture of these buds on BM + 0.5 mg/l BAP + 0.5 mg/l gibberellic acid (GA). Roots were induced in shoots longer than 3 em, cultured under red light (660 nm) on BM + 2.0 mg/l IBA. Forty percent of the regenerated plants were lost when transferred to soil. Surviving plants were kept under controlled conditions with 70-80% relative humidty and low light intensity (36. mu mol/seg(-1) m(-2)) for 4 weeks and were gradually hardened by transferring them to less protected conditions. In vitro regeneration of both rootstocks demanded 15 weeks. Hardening demanded 18 weeks on average.