iTunes won't import AIFF files

I've just started using Audacity to digitise some old lps. I've successfully recorded an album and divided it up into separate tracks. They are sitting in the Music folder on my hard drive as AIFF files. I've tried to add them to iTunes using 'Import', 'Add to library' and by dragging them and dropping them in but none of those routes works. According to iTunes help and Audacity help any of those methods should be fine. What am I doing wrong?