Marc
You didn't mention whether your table has multiple one-to-many relationships
with others, or if other tables (multiple) have one-to-many relationship
with your table. Either is possible and common.
What you cannot do is establish a many-to-many relationship -- for this,
you'll need a "junction" (or "relationship" or "resolver", or ...) table.
It will have a one-to-many relationship to each one of the tables that had
the original many-to-many.
If this hasn't answered your question, please post back a description of the
specific tables you are considering.