The existence of ringlike structures associated with diesel injection into liquid is clearly indicated in the article. This phenomenon has been found to be typical under injection conditions involving small amounts of injected fuel for all investigated diesel nozzles injecting liquid into liquid. An initial model of surface instability in the liquid leaving the nozzle is proposed as an explanation of the phenomenon. There are four characteristic phases selected to describe the process: phase 1 corresponds to formation of a jet or surface jet just after leaving the nozzle (no ring yet exists); in phase 2, a ringlike structure is formed at a given distance from the nozzle outlet; in phase 3, the ring structure strongly decelerates while moderately growing in size; phase 4 is characterized by a very stable slow motion of the ring. There are a number of additional features of the ringlike structures pointed out in the article. One very unusual behavior of the ring is its ability for off-axis motion. This process is random and is characterized by extreme deviation of the ring-propagation direction from the initial jet direction defined by the nozzle geometry. It is suggested in the article that the rings consist of individual gas bubbles, probably of a cavitational nature. As a consequence, it is assumed that the ringlike structures are related to the cavitation that is initiated inside the nozzle. Typical of the ring structures are their very long lifetime and stability. However, there are also observations made of rings quickly disappearing just after their generation.