Flue-cured tobacco production in Croatia, Yugoslavia, (25,000 tons/year) is exclusively based on growing F1 hybrids which possess tolerance to blue mold and black root rot. The parent materials for F1 hybrids were numerous American flue-cured tobacco varieties and Australian tobacco lines derived from crosses with Nicotiana goodspeedii and N. debneyi. Compared with standard American flue-cured tobacco varieties, F1 hybrids showed tolerance to blue mold and better vigor, so the farmers prefer such seeds. A number of farm tests and field experiments at different locations were carried out for evaluation of the hybrids, especially for agronomic properties. Nine F1 hybrids were chosen in 1980 and ten in 1981, and these were compared for agronomic and chemical properties with the standard variety NC 2326. In 1980, the yield ranged from 2134 to 2594 kg/ha; in 1981, due to the dry season, the yield dropped and ranged from 1884 to 2320 kg/ha. The most widespread hybrid used by farmers, Podravina (H 10), had the highest yield in 1981, 2320 kg/ha (NC 2326 yielded 2040 kg/ha). In 1980, the same hybrid was the second in yield. The other promising crosses are Speight G-28 x GV3, H-30, H-31, Coker 347 X GV3, and Coker 411 X GV3. Five of the crosses are taller than NC 2326, but hybrids with the American flue-cured varieties are not much different in field appearance from NC 2326. Nicotine content in 1980 ranged from 1.97 to 3.44%, while in the drier 1981 season, it ranged from 2.52 to 4.51%; total nitrogen ranged from 1.94 to 3.19 and 2.13 to 2.80% for 1980 and 1981, respectively. Nevertheless, the nicotine content was high; the percentage of reducing sugar was also high, ranging from 14.61 to 23.86% in 1980 and from 15.32 to 26.57% in 1981. Percentage of nornicotine was below 5% of the total alkaloids except for the hybrid H2-Zagreb, which is the only one with a very high nornicotine content, due to the inheritance of one parent from N. debneyi. For this reason this hybrid was not allowed for commercial production.