I was wondering if any other of Colt's 38 special barrels would fit safely on a police positive special, I have one that's in great condition except for the barrel, which is a bit pitted all throughout. I'd like to replace it, but PPS barrels seem to be quite a bit harder to come by than other d-frame barrels. Would any other other d-frame 38 special barrels fit on it?

Most any Colt "D" frame barrel will fit, as long as the front sight height is compatible.

The problem is, barrel changes are a QUALIFIED gunsmith job ONLY.
Attempting a barrel change with the old hammer-handle-through-the-frame trick WILL damage and/or ruin the gun.

Revolver barrels require a LOT of fitting and adjusting, and this requires some expensive tooling, ranging from a lathe, to a special frame wrench with inserts, to tooling used to re-cut the forcing cone, to special gages.
In other words, unless you're prepared to shell out several hundred dollars MINIMUM and spend the time to learn how to do the job, all you'll do is ruin a nice Colt.

Another problem is finding a good, USABLE barrel.  
A lot of the barrels you find online and at gun shows are defective, and this is not always detectable until you try to install it.

Good sources for barrels are:
Gun Parts, who carry most of the small frame Colt barrels.  (Note that they often list PPS barrels as "Detective Special" barrels).
www.e-gunparts.com/model.asp?idDept=50

Also, Jack First is a prime source of high quality parts.
www.jackfirstgun.com/

Thanks a lot, that was about as comprehensive an answer as I could hope to expect ;)

I'll check out those sites and see what they've got, then ask my gunsmith what he thinks once I get a chance

Colt don't have any more barrels?

Colt is getting low or is out of revolver barrels, especially for the older models.
Most of what they have they are saving for customer work.

dfariswheel: I have brush SS Python barrel that I'm using as a paper wieght because it came to me attached to the frame a bit canted, I think the guy who assembled my gun twisted just a bit too far, Colt replaced it under their warranty and I asked them to return the barrel to me as a souvenair.  Anyways, is there is a way to make the barrel good anymore?  Personally I can't tell there was any thing amiss just by looking at the barrel.  I noticed that it shot to once side and I had to move the sight over quite a bit, but I thought it was just me. I don't remember which side, it was something like 20 years ago.

BTW: Don't worry, I am not so unscrupulous that I'm going to foist it to some poor soul on eBay, it is definitely staying on my desk as a paper weight where it belongs.

If it was actually the barrel that was "off' somehow, there's nothing that can be done.

About all that could be done to check, is to test install it in a known good frame and look for problems.

Quoted: If it was actually the barrel that was "off' somehow, there's nothing that can be done. About all that could be done to check, is to test install it in a known good frame and look for problems.

Well, I think I'm just going to keep it on my desk, at some point way in the future, there won't be anymore Colt Python barrels left, and I will just have to endure the canted sights.  Probably won't be my problem because I only shoot 38spls out of mine, and when shooting lead, barrels last a long time.  Maybe my future great gradnson

By "canted" do you mean the barrel was pointing off to the side or installed in the frame crooked, or was it that the barrel didn't have the front sight sitting at 12:00 O'clock top-dead-center?

If the front sight wasn't aligned properly, the barrel is likely a usable barrel.
Usually Colt would simply refit the barrel to the frame, unless it was faster to just install a new one.

You might want to take a good look at it, it just might be a good barrel.

Quoted: . . was it that the barrel didn't have the front sight sitting at 12:00 O'clock top-dead-center? If the front sight wasn't aligned properly, the barrel is likely a usable barrel. Usually Colt would simply refit the barrel to the frame, unless it was faster to just install a new one. You might want to take a good look at it, it just might be a good barrel.

This sight wasn't position on the barrel at the 12o'clock position.
Nope, they gave me a brand new barrel, and I asked them and they told me you can have the old barrel if you want it..  So I kept the old barrel.  Back then it was probably faster just to put on a new barrel rather than fix the old one.  Their 'smiths were probably loaded with work.  But I think today Colt would've fixed it, rather than put on a new barrel.  This barrel is ~20 years old, I put ~1,000 rounds through it.  The thing is not even broken in.