A pentanuclear dysprosium hydroxy cluster of composition [Dy-5(mu(4)-OH)(mu(3)-OH)(4)(mu-eta(2)-Ph(2)acac)(4)(eta(2)-Ph(2)acac)(6)] (1; Ph(2)acac = dibenzoylmethanide) was prepared starting from [DyCl3 center dot 6H(2)O] and dibenzoyl methane. Both static (dc) and dynamic (ac) magnetic properties of 1 have been studied. Below 3 K, the appearance of slow relaxation of the magnetization typical for single-molecule magnets is seen, even if no hysteresis effects on the M vs H data are observed above 1.8 K.