Acetoxycycloheximide (AXM) or dibutyryl cyclic AMP (dbcAMP) was injected unilaterally into the vitreous humor of the eye beginning 5-6 days after bilateral optic nerve crush. Injections were repeated every 12-24 h for a total of 3-5 days; goldfish were sacrificed 10 days after lesioning the nerves. At a low dosage of AXM (0.1 microgram daily for 5 days), the mean outgrowth distance in treated neurons was 60% less than in contralateral control neurons. At a high dosage (0.3 microgram daily for 4 days), outgrowth was immediately blocked in both treated and contralateral control axons. Dibutyryl cyclic AMP, in a dose of 5 microM every 12 h for 3 days, produced a 38% reduction in outgrowth distance, associated with a 30% reduction in protein synthesis by the retinal ganglion cells and a 73% reduction in the amount of protein carried by the fast component of axonal transport.