The present investigation was undertaken to fabricate porous nanoparticles of metoprolol tartrate by spray-drying using ammonium carbonate as pore former. Prepared nanoparticles were coated with Eudragit S100 polymer in order to prevent the release of metoprolol tartrate in the upper GI tract. It was shown that nanoparticles with low size ranges can be obtained with a low feed inlet rate. Micromeritic studies confirmed that nanoparticle batches are discrete and free flowing. Effects of the pore former on drug loading, porosity and in vitro release were studied. It was found that there was an increase in drug loading and porosity with increasing the amount of pore former. In vitro drug release studies showed that an increase in pore former made drug release faster. Release kinetics proved that nanoparticles follow a zero-order release mechanism. U radu je opisana priprava poroznih nano~estica metoprolol tartarata pomo}u su{enja sprejanjem, koriste}i amonijev karbonat za stvaranje pora. Da bi se sprije~ilo osloba- |anje metoprolol tartarata u gornjem dijelu GI trakta, nano~estice su oblo`ene polimerom Eudragit S100. Nano~estice podjednake veli~ine mogu se dobiti polaganim uklapanjem ljekovite tvari. Mikromeri~ke studije potvrdile su da su nano~estice zasebne i te~ne. Prou- ~avan je utjecaj sredstva za stvaranje pora na koli~inu uklopljenog lijeka, poroznost i invitro osloba|anje. Pove}anje koli~ine sredstva za stvaranje pora pove}ava koli~inu uklopljenog lijeka, poroznost i brzinu osloba|anja ljekovite tvari. Osloba|anje metoprolola slijedi kinetiku nultog reda