All garlic cultivars used for crop production in the UK are infected with two or more viruses. ISEM [immunosorbent EM] decoration tests have indicated that onion yellow dwarf (OYDV), leek yellow stripe and shallot latent viruses (SLV) infect some cultivars in various combinations with other unidentified poty- or carlaviruses. The shallot cv Noordhollandse Strogele was infected by OYDV, SLV and a second potyvirus. Virus-free plants of eight garlic cultivars and the shallot cv Noordhollandse Strogele were produced by meristem-tip culture. The percentage of virus-free garlic plants regenerated was increased from 25-50% to 85% when infected parent plants were subjected to thermotherapy at 38.degree. C prior to tissue culture.