To investigate current advice given to insulin-treated diabetic patients undertaking international flights crossing time-zones, we have conducted a survey of UK physicians running diabetic clinics. Consultants were asked to give the general advice they would give to travellers on twice-daily short- and intermediate-acting insulins in four different flight situations: westward London to New York (morning and evening departures) and eastward Manchester to Singapore (morning and evening departures). Response rate was poor (37%). Six percent of replies were unhelpful (e.g. 'ring the BDA', 'carry on as usual'), and 14% liable to cause hypoglycaemia. Thirteen percent advocated change to a 'basal-bolus' system of insulin administration. The rest used variants of additional insulin for westward flights and reduced flights eastward. There was great variation in advice, and many regimens were excessively complicated. We recommend simple individualized advice, without attempts at over-zealous glycaemic control during travel. Local arrival and departure times may fit in easily with insulin and meals at standard times before and after flying, and little or no dosage alteration may be needed.