Former World Cup and Olympic champion Janica Kostelic will race for the first time before her home crowd.
Ski fever has transformed Croatia's capital into a ski resort. Zagreb is draped in national flags and skiing posters. A stage with a gigantic video wall in the main square will host top local bands who will entertain thousands of spectators on Thursday.
The public expects much of Kostelic, who has recovered this season after a year-long break.
Kostelic has made an astonishing comeback since losing the whole of last season to a succession of knee injuries and a surgery to remove her thyroid.
She won the season's opening slalom in Aspen and has been on the winners' podium on four other occasions.
Security will be a crucial issue during the Sljeme race. The slope will be monitored by three mountain rescue helicopters, 800 soldiers, 800 police, as well as private security.
Prime Minister Ivo Sanader and President Stjepan Mesic are expected to attend.
Kostelic's brother Ivica, world champion in slalom, will be one of the forerunners.
The first 10,000 tickets were sold out as soon as they went on sale last week and organisers say they expect up to 24,000 spectators.
Local radio stations are urging citizens to come to Sljeme, a popular weekend destination overlooking Zagreb.
Kostelic can take the overall World Cup lead as well, just by staying sufficiently ahead of closest slalom rivals Tanja Poutiainen and Anja Paerson.