Importing particular categories

Hi,

I am moving my old WordPress Blog to a new WordPress Blog, but only wished to move across certain categories of post, so I was going to import/export each category I required.

I have used exported/imported one category and then it suddenly occurred to me that because certain posts had two categories, such as “quackery” and “Pharmacy” that that post might be imported twice.

Is this true? and what is the best way round it?

Anthony