We find a general solution $f:G{ ightarrow}G$ of the symmetric functional equation $$x+f(y+f(x))=y+f(x+f(y)),;f(0)=0$$ where G is a 2-divisible abelian group. We also prove that there exists no measurable solution $f:mathbb{R}{ ightarrow}mathbb{R}$ of the equation. We also find the continuous solutions $f:mathbb{C}{ ightarrow}mathbb{C}$ of the equation.