The autor considers the population development of Zagreb since its origins, concentrating on the period from the 1850s to the last population census (1991). In the 1450s Gradec had about 3,500 and Kaptol about 1,000 inhabitants. At the time when the two separate town jurisdictions were united (1850) Zagreb had about 15,000 inhabitants. Since than the town has grown territorially and gone through very dynamic development. A retrospect of the more limited urban area (»10 urban municipalities«) shows that Zagreb’s population grew eighteen and a half times in the 1857-991 period (in 1991 Zagreb had 721,136 inhabitants). Zagreb has been attracting people since its beginnings; immigration played an major role in the population development of the city. Of the total population increase in the 1880-1991 period, 27 per cent stems from natural increase and 73 per cent from net migration! In 1880 Zagreb’s citizens included 68 per cent immigrants; since the Second World War their participation has been decreasing, and in the last census (1991) it was barely 50 per cent! The aggression on Croatia and the war on its soil speeded up demographic processes which will, combined with other factors, step up immigration, thus increasing the city population’s rate of growth and the participation of immigrant citizens in the total population of the city