One thing to keep in mind is that, in a conventional western piece of music, the I, IV and V chords are typically major, while the II, III and VI chords are typically minor. So when someone refers to a I-VI-II-V progression (As M.Ted did above), he really means I-VIm-IIm-V. M.Ted only did this halfway, which resulted in mousethief's confusion. Nashville cats tend to add in the "m" to indicate minor when they're preparing their charts, while classically-trained musicians (like Don firth) would probably say that this is implied by the numbers themselves.

Am I making sense to anybody?