Single crystals of HoAl 3(BO 3) 4 were flux grown and their principal magnetic susceptibilities, parallel and perpendicular to the symmetry axis of the crystal, χ ‖ and χ ⊥, measured in the range 300-14.5 K. The principal anisotropy χ ‖- χ ⊥ turns out to be positive throughout. A theoretical analysis of the experimental results invoking the crystal field interaction of the Ho 3+ ion with D 3 site symmetry, obtained from structural data, provide an excellent explanation of the observed behavior of the ion over the entire temperature range in our study; this rules out exchange or dipolar effects of any significance down to 14.5 K. The energy level structure of this potential laser crystal for all the low lying multiplets of the ground term is given and the anomalies in the electronic heat capacity located. The quadrupole splitting of 165Ho due to crystal field effects has been computed, which gives rise to a peak in the hyperfine heat capacity at about 5.5 mK.