ABSTRACT Our objective is to elucidate the influence of oxygen on the spatial distribution of the benthic fauna in shallow waters. In this study, our attention was focussed on the Chironomidae that are abundant in our study site - a small euthrohic pond in Belgium. It is well known that oxygen controls the specific occurence and macrodistribution of chironomid larvae in standing waters (Heinis, 1993). However, it is unclear how the "respiratory environment" (Brundin, 1951) of these organisms is defined. Our study of the oxygen microstratification is intended to elucidate its significance for the vertical distribution of the chironomid larvae. Therefore, we have measured the oxygen concentration at several locations above and in the sediment as well as in the water column.