Abstract: The invention concerns a process and apparatus wherein the paraffin effluent from the Fischer-Tropsch process is separated into a heavy fraction with an initial boiling point of 120-200° C., said heavy fraction then optionally being hydrotreated then brought into contact with an amorphous hydroisomerization/hydrocracking catalyst that converts at least 80% by weight of the 370° C.+ products into products with a boiling point of less than 370° C. After distilling the hydrocracked fraction obtained to separate middle distillates, the residual heavy fraction is recycled.