The goal of treatment for a Hemophiliac patient is to replace the deficient coagulation factor (Factor VIII or IX depending on the type of Hemophilia present).  Factor replacement can be given on an "as needed" basis or routinely to maintain constant coagulation factors in the blood.

Factor VIII used to be "pooled" from a large number of blood donors.  The problem with this is the patient was at risk for blood borne disease.  The medicine was made from an estimated 10,000 or more donors!  It is believed that 3 companies paid prisoners and drug-addicts for the donation of their plasma.  These donors were at high risk for Hepatitis C and HIV (the virus that causes aids).  No one knew about HIV in the late 1970s and early 1980s so blood products were not screened for this deadly virus.  Consequently, the HIV virus nearly wiped out the entire population of individuals with Hemophilia.

Recently, molecular genetics has played an important role in producing a recombinant factor replacement.
In this technique, the genes producing the missing factor are "cloned"  and placed into bacteria genes.  The bacteria now produce the factor replacement.  Because bacteria reproduce rapidly, large amounts of factor can be manufactured, free of any viral contaminant. 

Scientists are currently experimenting with using genetic engineering as a "cure."  Genes that produce the missing factor (in this case Factor VIII), are inserted by viral vectors into the patient's cells.   The patient's own cells now begin to produce the missing factor.  This method is currently being tested in humans.  See Gene Therapy for Hemophilia

*Information taken from "Hemophilia-Factor VIII Deficiency,"  Donna M. DiMichele and David Green and
"Contaminated Hemophilia Products."  http://en.wikipedia.org/wiki/Contaminated_haemophilia_blood_products