Abstract. We study the periodic solutions of the generalized Abel equation x ′ = a1A1(t)x n 1 +a2A2(t)x n 2 +a3A3(t)x n 3 , where n1, n2, n3 > 1 are distinct integers, a1, a2, a3 ∈ R, and A1, A2, A3 are 2π-periodic analytic functions such that A1(t) sin t, A2(t) cos t, A3(t) sin t cos t are π-periodic positive even functions.When (n3 − n1)(n3 − n2) < 0 we prove that the equation has no nontrivial (different from zero) limit cycle for any value of the parameters a1, a2, a3.When (n3 − n1)(n3 − n2) > 0 we obtain under additional conditions the existence of non-trivial limit cycles. In particular, we obtain limit cycles not detected by Abelian integrals.