We have studied the growth of neurites from single retinal ganglion cells isolated from adult goldfish and maintained under various primary cell culture conditions. In 10% Leibovitz's L-15 medium at 23 degrees C, these ganglion cells remained viable for up to 10 days and generated extensive fields of neurites. We found two patterns of neuritic fields. In one, a pair of neurites exited from opposite sides of the cell soma, forming a bipolar pattern. In the second pattern, three to five neurites exited from several points around the soma, forming a multipolar pattern. Characteristically, each neurite of this latter type tapered and branched two to seven times, whereas neurites forming bipolar patterns showed less branching and little or no taper. The fields subtended by the neurites in multipolar patterns ranged in size from 33,000 to 204,000 microns 2. Finally, although these neurites grew as fast as 35 microns hr-1 at 23 degrees C and individually reached lengths of up to 735 microns, they showed essentially no growth at 13 degrees C. Neurite outgrowth at 23 degrees C was vigorous even in cells whose growth had previously been suppressed for as long as 8 hr at 13 degrees C.