The potential benefits of aseptic culture techniques for bananas and plantains are considerable. The challenge is, as in other plants, to develop highly reliable methods. As well as effective shoot tip, apical meristem, callus, cell and protoplast culture methods, this means that, sooner or later, in vitro-derived or -manipulated materials must be grown to maturity in the field and properly evaluated. Economic considerations will then determine actual use. Information from preliminary field trials is just beginning to emerge. The status of the subject is uncertain and will remain so until better information is available. Some trials have shown an unacceptably high level of "off-types" of unknown causation. This letter is an attempt to review the problem. Suggestions are made for a revision of ideas on achieving the required reliability, and a call is made to communicate experiences with tissue culture-derived plantings of bananas and plantains. Special emphasis should be given to numbers of plants evaluated, to stability or lack thereof and to recurrence of plant-crop effects in the ratoon.