Throw up-what to do?

I found what looks like cat throw up.  But it looks weird because the food pellets are still whole--as if they haven't been digested.  I have two cats so I'm not sure which one it is, but for the most part they both seem healthy.  

What should I do?  Is throwing up a big concern?  Should I take them to the vet?  

Throwing up isn't a huge concern on its own. It can happen when the cat in question eats too much too quickly. Especially if you saw identifiable pieces of food it was probably just eating too much. It could also be that one has a hairball on the way or a sensitivity to something they are eating. One of mine throws up at least once a week.

Just keep an eye on them. It was most likely a one off occurrence. If you notice more frequent vomiting, diarrhea, lethargic behavior or vomiting blood or bile you should make an appointment.  

Ok thanks very much!!

Kieka is absolutely right that an occasional pile of throw-up is nothing to worry about.  My Chula eats too fast sometimes and the result is a pile that looks very much like what you describe, i.e. undigested food.  There are ways to prevent cats from eating too quickly.  Try raising their bowls up a few inches or putting a golf ball or overturned glass in the middle of the bowl.  This forces the food out to the edge.  If you are feeding them dried food, you might even invest in a food maze where they have to actually work at getting the food out.

As Kieka says keep an eye on them and if you notice any of the symptoms she mentions, take them to the vet.  Hopefully this is nothing serious.  

Thanks good to know!!