The effects of the massive Japanese earthquake and tsunami in March are thought to have skewed new car sales in May.
The 4535 new cars sold last month were down 1.8 per cent on a year earlier, although 277 ahead of the April figures.
Motor Industry Association chief executive Perry Kerr said the overall total last month, as well as brand rankings, had been affected by shortages of new vehicle stock.
After the new vehicle industry had started the year strongly, the supply of some vehicle models had been disrupted as a consequence of the March tsunami.
But recent reports indicated the Japanese industry was moving more quickly than originally expected and the association was hopeful supply would be back to normal by the fourth quarter.
Normally dominant company Toyota, which made 20 per cent of new car sales in 2010, was in sixth place in May with just 331 sales or 7.3 per cent of the new car market.
Holden was in first place with 560 sales or 12.4 per cent, followed by Hyundai with 454 sales or 10 per cent, and Suzuki with 433 sales or 9.6 per cent.
Only 88 Toyota Corollas were sold in May, compared to 286 Suzuki Swifts, 205 Holden Commodores, 181 Holden Captivas and 173 Hyundai I30s.
Commercial vehicles made a strong showing last month, with the 2028 sales of new commercials below only two other months in the past two years, and 12.6 per cent ahead of a year earlier.
Toyota led the commercial segment with 632 registrations followed by Nissan with 347 and Ford with 270.
Light commercial vehicles were the top two selling models overall for the month, with the Toyota Hilux at 450 and the Nissan Navara at 337. The third selling light commercial was the Ford Ranger at 208.
That trend is expected to continue through June with a strong sales push around the National Agricultural Fieldays, Kerr said.
The 7013 used car registrations, usually imported used cars, were 14 per cent up from April and 5 per cent down from May 2010.