Gastric emptying of a test meal labelled with 99Tcm-sulphur colloid has been studied in 9 healthy volunteers using a gamma-camera with on-line computer. Mean transit time (MTT) was determined by fitting the time-activity histogram to a gamma-variate, and the half-time of emptying (T½) was calculated by exponential fitting of the down-slope of the time-activity curve. MTT showed a smaller coefficient of variance than T½ This result suggests that MTT may be a more suitable parameter for definition of normal values and for the separation of normal from pathological patterns of emptyin