How can I tell if they are playing or fighting?

MY cats wrestle around but they don't hiss or growl when they do it. Are they playing? sometimes I guess one will get to rough and I hear a loud meow and they both run away and that's the end of it.

I take it as a sign of playing. My cats stalk each other around the couch and then its up and down the hallway. It usually calms into a cleaning session. The two are littermates and have been acting that way around each other their entire lives. I only worry once I hear hissing.

And now after reading your signature I have 'Into the Woods' running through my head. heh.

What your kitties are doing is playing.

Some play fights do include hissing and growling.

Think of your stereotypical cat fight? Got it? Loud meows, (closer to howling), flying fur and claws blazed? That is time to step in. But please, not with a bucket of water. That equals huge mess and scared cats.

Drop a large heavy dark blanket over the both of them. That should startle them and cause them to stop what they're doing. If the agression is still present, separate the kitties for a short time, say five minutes in a room with the door closed. After 5 minutes open the doors and let the kitties come out in their own time.

It looks a bit rough at times when my pair play- but as there is never hissing or growling- and either of them could get away if they wanted to I don't worry.
There is the occasional distressed meow from one- then the other one backs off.
I think the best sign is when one of them will roll over and go to sleep belly up immediately afterwards!
Cheers
catherine