Hyundai and its affiliate Kia sold over 100,000 hybrids in the U.S.
Hyundai's Sonata hybrid was released in April 2011 two months before Kia's K5 hybrid.
Since then, some 65,263 Sonatas and 34,748 K5s were sold. Sales rose from 13,491 units in the first year to 37,158 units last year.
In July this year the Sonata posted record monthly sales of 2,800 units there, amid a 10 percent on-year drop in the U.S. hybrid market.
"Further increases in sales are expected as new hybrid models will hit the market early next year," a Hyundai spokesman said.