After evaluation of the essential parameters concerning urinary calculi and patient with the help of adequate computer programmes in more than 30,000 persons some conspicious trends could be established. The necessity of operative removal of calculi is still relatively high in the most frequent species of calculi whewellite, weddellite, uric acid, struvite and carbonate apatite. Thus nearly 65% of all struvite and carbonate apatite calculi must be operatively removed in women. For individual species of stones with statistical certainty (alpha=0.01) the preference of the right kidney in women and of the left kidney in men is established. The summer months bring an increased risk of stone formation. The spontaneous passages show a highly significant increase from July to October (alpha=0.01), compared with the winter and spring months.