Struvite crystals were pptd. from aq. soln. of NH4H2PO4, MgCl2 center dot 6H(2)O and KCl (PO43-:Mg2+:NH4+ mole ratio 1:1:1 to 1:1.2:1) at 298 K and pH 9-11 for 900-3600 s in lab. crystalizer (draft tube mixed suspension mixed product removal type). The presence of K+ ions resulted in an improvement of the product quality. Homogeneity was increased by 10% and mean size of the crystals by ca. 43%.