I practice slowly and firmly with long short longs, and then short long shorts. I go all the way thru the passage with the pattern long short long short long, etc….next time thru the passage with the pattern short long short long short, etc….then back to the other pattern…back and forth as long as I can stand it….slowly and placing firmly.

When I put it with the metronome, I go back and forth from slower to faster, slower to faster, and try to eventually take it faster than tempo, so that going back to tempo feels comfortable and stays clean with no noise between notes.

Like Gretchen, I practice them as block chords and get the block chords up to tempo first. You can also practice just with just the thumbs. Karen Vaughan gives advice on practicing the Swan Lake arpeggios at @http://www.youtube.com/watch?v=6JZcHSSQbD8&t=2m37s.
If the arpeggios are all triads, you might try them with both 3 and 4 fingers and see which is easier. Four fingers gives you fewer crossings to worry about, but three fingers means you’re playing an identical set of notes each time, which makes placing them much easier.

The suggestions here are good. But I’m not sure they answer your basic question, which is how to pay hand over hand arpeggios evenly. Here is the basic technique and practice routine to master arpeggios.

Let’s say you are going to work on a 4 octave, hand over hand, arpeggio, using all 4 fingers of both hands.

1) start by learning to play the hand positions as chords. Practice one hand at a time, going up the instrument, playing root position, first inversion, second inversion, root position, etc. Then learn to do that with both hands. Then play the chords hand over hand up and down 4 octaves. Start first with the left hand in root position, then do it again with the left hand starting in first inversion, etc. The goal through all of this is to place all 4 fingers simultaneously, and have the 4 finger tips touch the strings exactly where they are going to play. No adjusting after you’ve placed. The last step of this first stage is to do all of these things, touching the strings at the moment you play and not a nanosecond earlier.

2) Now start playing a hand over hand arpeggio. Play it in many variations: uneven rhythm(short, long, short, etc),groups of two, groups of 3, etc. Also try playing them evenly, but accenting every other note, or every third note. The accent should be FF, and the other notes pp. This is the way to get the arpeggio absolutely even.

Yes Gretchen, I realize I repeated what was said in a couple of other posts. But to get evenness in the arpeggio, you have to practice in uneven rhythms and uneven accents. That oddly enough is how you get all of the fingers to play evenly. I would add one more thing to practicing chord patterns. When you practice with both hands, spend some time playing chord positions with the left hand ABOVE the right, so that, in a grand arpeggio, that position feels comfortable.

Loon, are you overwhelmed with advice:)

Loon- You can use the same type of exercises to work on scales too. It sounds like you are at a point where you are noticing an unevenness in the way your fingers work. The exercises I suggested will do the trick if you do them correctly. Do you have a teacher?

Yes, I totally agree with Carl about playing in different rhythms and accents. This is how we had to practice all of Tchaikovsky’s. cadenzas (we learned them all together) when I was at college. The best advice we were given was to avoid playing any rhythm that came easily – that’s most likely the one you slip into when things get uneven. Also play in triplets, 5s and 7s because they don’t come naturally to most people. Another thing we did was to repeat every finger twice, while also playing in triplets. I remember being able to play the while of Hasselmans La Source his way. Repeating every single note but accenting in triplets. I did it for fun. Must have been mad!!! (It was bloomin’ even though ;))