Nutrient assimilation and metabolism in sunflower leaves were examined in both btealthy and Alternaria helianthi infected plants. An increase in the total nitrogen and accumula tion of ammonia was observed in the Ahemaia infected leaves. The nitrate accumulation following infection was found to be non-significant. A significant increase in total phosphorus was observed in infected leaves whereas the available phosphorus contents was reduced drastically. The deamination of aspartic acid, glutamic acid, tyiosine and arginine in vivo was found to be significantly higher in infected leaves than healthy ones. The nitrite and nitrate reductase activitieswere found to be higher in infected leaves. Whereâs the ratio ofchlorophyll a/b was higherin healthy leaves. The soluble sugar contentwas observed to be more in infectêd than the healthy leaves ofsunflower. The possible explanations for these alterations in nutrient metabolism of sunflower leaves infected with Alternaria have been discussed.