13C-breath tests are modern diagnostic tools for evaluation of dynamic processes in the human body. 13C-octanoic acid breath tests enable us to examine gastric emptying even in children including neonates, and pregnant women. The approach to mathematical processing of elimination 13CO2 and calculation of gastric emptying parameters has not been standardized and is not unequivocal. The paper presents a review of different methods of gastric emptying evaluation that use breath tests. The authors mention methodological difficulties, different approaches, and various definitions, that may be found both in scintigraphy as a referencemethod and in breath tests. The aim is to offer an easy orientation in the topic. The second part presents description of evaluation of 13CO2 elimination. Parameters of incomplete gamma function are estimated by the moment method. The theoretical background is the idea, that empirical δ values are proportional to the density of the distribution. Application of the moment method enables us to avoid computational pitfalls of a non-linear regression model, especially the question of the existence of minima and non-availability of initial solution for iterative processes.

        Key words: 13C-octanoic acid breath test, gastric emptying, mathematical model.