We investigate the possible occurence of chaotic motion at the secular resonances v5, v6 and v16 integrating model asteroids and known asteroids over some Myrs. At the resonances v6 and v16 we findt ransitions between libration, inner and outer circulation. Such transitions are in the case of mean motions resonances related to chaotic motion. Chaotic motion is also indicated by a temporary location in both resonances, v6 and v16, as well as in the resonances v5 and v16. Chaotic motion is also indicated by close approaches to Jupiter like in the case of the v6 resonant asteroid (2368) Beltovata. The calculation of corresponding maximum Lyapunov exponents would confirm our conjecture concerning the occurence of chaotic motion at secular resonances.