Small-interval water sampling in oceanic subsurface layers in a variety of macroenvironments for microplankton and for characteristics of their environment revealed concentration variations that often exceed errors of sampling and measurement. I report incidence and degree of microscale and finescale organism patchiness and their dependency on the local environment and on certain characteristics of the organisms themselves. Scale analysis indicates that patchiness occurs below as well as above the 20 cm intervals sampled. Incidence and degree of patchiness were about the same in separate eastern boundary regions, off California and Perú. Effects of environmental characteristics on organism patchiness are clearly defined in this data set, which suggests influences by physical processes on local microplankton patches on the scale of a few centimeters (microscale) to a few meters (finescale). In the aggregate, finescale and microscale patchiness of microplankton populations was greater at lower wind speeds, during daylight than at night, and over continental slopes. Patchiness was greater in the more stable layers of the seasonal pycnocline, and under more oligotrophic conditions (lower concentrations of nutrients, particulates, and chlorophylls). Patchiness of organisms also was greater where nutrients and particulates were more patchy, but was unrelated to chlorophyll patchiness. Intrinsic properties of the organisms less clearly affected microplankton patchiness. Population patchiness was greater for autotrophs and heterotrophs than for atrophs, and was slightly greater for larval fish competitors and predators than for their prey, and for more motile organisms. Reproductive capacity is indicated to dominate among intrinsic patch-forming attributes. Smallscale patchiness of small plankton is a recurrent feature of the environment of small predators and may affect their growth and survival. Its incidence and degree appear to be specifiable over large domains from parameters of the mixing environment, e.g. wind stress and vertical stability. This would contribute to management of exploited stocks of marine organisms whose recruitment depends on food supply at early stages of their life-history.