Mission Valley is enjoying an upswing in popularity among tenants, causing vacancies to plummet and rents to rise--a welcome development among building owners who so far have not fared as well as their North County colleagues in the county's recent office boom.

The market is composed of 95 office buildings totaling about 5.6 million sf, according to Richard Gonar, an office broker with Business Real Estate Brokerage Co. But the area has very little room to grow, ensuring that rates will remain high, as long as the economy stays strong.

"Mission Valley's lack of available space combined with the lack of developable land, has helped drive up rental rates across the board tolevels unseen in more than a decade," Gonar says.