It has been suggested that obesity is associated with an altered rate of gastric emptying, and that there are also sex differences in gastric emptying. The results of earlier studies examining gastric emptying rates in obesity and in males and females have proved inconsistent. The aim of this study was to investigate the influence of obesity and gender on gastric emptying, by extending conventional evaluation methods with Kaplan-Meier plots, in order to assess whether these factors have to be accounted for when interpreting results of scintigraphic gastric emptying tests. Twenty-one normal-weight volunteers and nine obese subjects were fed a standardised technetium-99m labelled albumin omelette. Imaging data were acquired at 5- and 10-min intervals in both posterior and anterior projections with the subjects in the sitting position. The half-emptying time, analysed by Kaplan-Meier plot (log-rank test), were shorter in obese subjects compared to normal-weight subjects and later in females compared to males. Also, the lag-phase and half-emptying time were shorter in obese females than in normal females. This study shows an association between different gastric emptying rates and obesity and gender. Therefore, body mass index and gender have to be accounted for when interpreting results of scintigraphic gastric emptying studies.