Abstract. Let F be an infinitesimal generator of a semigroup of holomorphic self-maps in a smooth strongly convex subdomain D of C n . We prove that F ≡ 0 on D if F vanishes in angualr sense at a boundary point up to third order.A semigroup Φ t of holomorphic maps in a subdomain D of C n is a continuous homomorphism from the additive semigroup (R + , +) into the semigroup Hol (D,D) of holomorphic self-maps of D, respect to the operation of composition, endowed with the topology of uniform convergence on compacts subsets. We know ( [2, Section 2.5.3], [24] and [22]) that the function [0, +∞) ∋ t → Φ t ∈ Hol (D, D) is analytic, and that to each such semigroup there corresponds a vector field F : D → C n (as usual we identify C n with its tangent space), such that ∂Φt ∂t = F (Φ t ) (It should be noted that the book [24] uses a different sign convention, so some formulas may appear a bit different). This vector field is usually called the infinitesimal generator of the semigroup. It is a semicomplete vector field, in the sense that each maximal solution γ z , with γ(0) = z, can be extended up to +∞. On the other hand, let D be a subdomain of C n and F : D → C n a holomorphic map; if, for each z ∈ D, the Cauchy problem given by