Hello Yimfong, most medical school programs in the US are graduate programs, meaning that students must complete 4 years of undergraduate work before enrolling. There are some programs that are combined programs, meaning they combine the undergraduate and graduate years together, but most are graduate programs. Good luck.
I believe the original poster was asking about 6+ year programs right out of HS. There ARE several of these, highly competitive of course.
You can find a list in the AAMC Medical School Admissions Requirements, available at your nearest medical school bookstore or perhaps some astute reader will provide a free on-line link with a list of such programs.
Several places do offer "undergraduate" medical programs - 6 to 7 yr. programs. But...I'm not sure that it's very recommended to do them. NEOUCOM has one (north eastern ohio university) and Northwestern University might do one.