Feeding by adult females of Pseudocalanus minutus on naturally occurring particles was determined by comparing particle size spectra in the water and that removed from it as the ration. Mean diameters and variances computed for the overall particle spectra were similar in both water and ration. Cumulative frequencies of particle numbers and volumes computed for both water and ration were not significantly different in two thirds of the experiments. In one third of the experiments significant values were found, mainly due to addition of particles in the small size ranges, as a result of feeding. The hypothesis of nonselectivity by Pseudocalanus minutus was not rejected by the Kolmogorov-Smirnov’s test. It is suggested that when particle peaks occur copepods obtain a part of their ration from the most productive cells of the phytoplankton population.