The present invention discloses a method for treating HIV that includes administering .beta.-D-D4FC or its pharmaceutically acceptable salt or prodrug to a human in need of therapy in combination or alternation with a drug that induces a mutation in HIV-1 at a location other than the 70(K to N), 90 or the 172 codons of the reverse transcriptase region. Also disclosed is a method for using .beta.-D-D4FC as "salvage therapy" to patients which exhibit drug resistance to other anti-HIV agents. .beta.-D-D4FC can be used generally as salvage therapy for any patient which exhibits resistance to a drug that induces a mutation at other than the 70(K to N), 90 or the 172 codons.