This study was designed to find out the effects of $omega$-3 and $omega$-6 polyunsaturated and saturated fatty acid from prenatal to growing period on the brain growth and behavioral development of rats. Rats(Sprague-Dawley strain) were fed experimental diets-fish oil, corn oil or beef tallow-with different contents of $omega$-3 and $omega$-6 fatty acids throughout the prenatal and lactational period and up to 10 weeks of age. DNA and RNA concentration of rat brain were determined at 0, 3, 6 weeks of age and choline and acetylcholine concentrations were analyzed at 10 weeks of age. When the rats were 7 weeks of age, position reversional test in a Y-shaped water maze for 4 weeks was measured. The experimental results obtained are summarized as follows. Food intakes were significantly lower in fish oil group and body weight gain was low in the group fed beef tallow and the groups fed fish oil and corn oil were somewhat good. Food efficiency ratio was not significantly different among the groups. Brain weight was not affected by the fatty acid composition of experimental diets and DNA and RNA concentration of the rat brain were consistently maintained at the same level. It was not different significantly among the dietary groups in the DNA and RNA concentrations of the rat brain during the experimental period. The acetylcholine concentration in the fish oil group was somewhat higher than the other groups. The position reversional test in a Y-shaped water maze showed a significant difference the score of test among the experimental groups. The score of the rats fed the fish oil diet was significantly higher than the other groups and the concentration of acetylcholine in brain were too. Therefore the correlatin between the Y-shaped water maze test score and the acetylcholine concentratin in the brain was found. Above finding support the content that dietary fatty acid composition does not affect to the brain cell number and cell size but the behavior development is influenced. Therefore, the improvement of behavior development is required the effective usage of finny tribe.