From photographic recordings the distribution of individuals of the back swimmer Notonecta glauca in natural and artificial populations of various densities and sex ratios were analysed. The distances between each animal and its nearest neighbour were measured and compared with calculated data from population models with known dispersion patterns. It was shown that each back swimmer population with a higher density than 6 animals per m2 follows a random distribution. Varying the ratio of males to females in the population has no influence on the type of dispersion nor has age from 3. instar to imago. In populations with smaller densities than 7 animals per m2 the difference in average interindividual distance between a random dispersion model and a uniform dispersion model is not significant for each density. Therefore it is impossible to decide whether Notonecta-populations with these low densities are randomly or uniformly distributed. The agreement of the dispersion pattern of the back swimmer populations with a random distribution indicates the absence of any behaviour affecting dispersion of this predatory water bug.