For any complex polynomial P (z) = c 0 +c 1 z +...+c n z n , c n = 0, having all its zeros in the unit disk |z| ≤ 1, we consider the behavior of the function (argP (e iθ )) ′ θ when the real argument θ changes. We give some sharp estimates of this function involving of the values of P (e iθ ), argP (e iθ ) or the coefficients c k , k = 0, 1, n − 1, n.