Long-chain polyunsaturated fatty acids (LCPUFA) are essential for proper neural and retinal development in many mammalian species. One objective of this research was to investigate the effects of dietary α-linolenic acid (ALA) and LCPUFA on the fatty acid composition of canine plasma phospholipids (PL) and milk during the gestation and lactation periods. The fatty acid composition of plasma PL and the retinal development of puppies reared on the same experimental diets as their mothers were also investigated. Enriching the canine gestation/lactation diet with ALA (6.8% DM) does not result in enrichment of docosahexaenoic acid (DHA) in the milk. From this data it can be inferred that peroxisomal elongation and desaturation of LCPUFA does not occur in canine mammary tissue. Dose responses of linoleic acid (LA), ALA and DHA were observed in the plasma of adult dogs during gestation and lactation and in puppies during both the suckling and post-weaning periods. Plasma PL fatty acid data from puppies indicate that canine neonates are capable of synthesizing LCPUFA from ALA, but that plasma enrichment of the newly-synthesized DHA does not compare with that obtained from preformed DHA in the diet. Visual function was assessed via electroretinography (ERG) in 12-wk old canines. One-way ANOVA revealed significantly better visual performance in dogs fed the highest amounts of n-3 LCPUFA. Puppies in this group demonstrated the greatest rod response as measured by the amplitude and implicit time of the a-wave. Neonates reared on the lowest dietary levels of both ALA and n-3 LCPUFA exhibited the poorest visual function. A novel parameter devised in this study was the threshold intensity, which was the initial intensity at which the a-wave was detectable. Again, puppies consuming the greatest concentrations of n-3 LCPUFA responded significantly sooner, i.e. exhibited greater rod sensitivity, than other diet groups. The findings of this research underscore the importance of preformed n-3 LCPUFA in the diet, rather than ALA, as a means of enriching neural tissues in DHA during the developmental period. Moreover, dietary DHA appears to be related to improved visual performance in developing canines.