Catch-up growth in coeliac disease was thought to be a continuous process and hence linear models have been proposed to interpret the pattern of catch-up growth. Observed longitudinal data do not fit a linear model adequately. The aim of this study is to clarify the pattern of short-term catch-up growth in coeliac patients. Twenty-one coeliac children (aged 6-24 months) entered the study and were monitored at short-time intervals. All showed a "pulsatile" pattern of growth velocity for height, weight, leg length, subscapular and triceps skinfolds. Peaks alternated with troughs at a mean time of 62 days for the whole set of measurements. The periodicity was remarkably stable. The size of the peaks decreased with time on a gluten-free diet. Catch-up growth is a discontinuous process made up of a sequence of bursts of growth followed by a resting phase. This provides strong evidence for the possibility that short-term growth may be pulsatile.