We've recently gotten the opportunity to aquire a darling M Jack Russell 4 month old. We've got a 2.5 year old F lab already. Is there anything to worry about between these two dogs? He's coming over the spend the day tomorrow and we'll see how they get along for several hours, but I realize this isn't necessarily going to tell us how they get along for the next several years. Thanks.
We've recently gotten the opportunity to aquire a darling M Jack Russell 4 month old. We've got a 2.5 year ... hours, but I realize this isn't necessarily going to tell us how they get along for the next several years.

I think that you're doing it right. A few hours of play can tell you plenty as to how they'll get along. You're doing what I did when I bought Friday into my home: Foster mom and I took him for an off-leash walk with my dogs and the next day I did agility with him. He was a keeper.
Really pay attention to the small stuff, especially the comfort level of your lab and how well she responds to puppy attacks.

Matt. Rocky's a Dog.
Is there anything to worry about between these two dogs?

Most likely not. Jacks and Labs are generally a fairly good combination, since both breeds tend to have a rough play style; my JRT gets along very well with most Labs. You DO have to be careful of the smaller dog getting stepped on.
What you should be worrying about, though, is whether you're up to living with a JRT- they're high-maintenence dogs, with an incredible energy level, tons of prey drive, and an independent streak.
We've recently gotten the opportunity to aquire a darling M Jack Russell 4 month old. We've got a 2.5 year ... but I realize this isn't necessarily going to tell us how they get along for the next several years. Thanks.

Greetings...
If you're thinking about a Jack, you have a lot more to concern yourself with than just whether or not it will get along with your other dog. First read this:
http://www.terrier.com/breed/baddog.php3
Then, if you're still considering it, try taking the JRT profiler: http://www.terrier.com/breed/jrprofiler.php3
Try to do this before you spend the day with the puppy. They're just darling little creatures, especially as pups, and it's easy to fall in love with them before you really think about your decidion. I know that the breed is NOT for me, but it may be right for you.

And don't forget that a puppy at 4 months old might get along with your dog now, but may show dog aggression as it reaches full maturity. Are you (and your house) prepared to keep them separated at all times if necessary?

Hope this helps ...
Kind Regards,
Tracy
If you're thinking about a Jack, you have a lot more to concern yourself with than just whether or not it will get along with your other dog. First read this: http://www.terrier.com/breed/baddog.php3

I've already been to that site and read about all as I could with a full Thanksgiving stomach after 9 o'clock. Emotion: smile
Since I don't have children yet, I take my dog(s) as seriously as most people take parenting. Lack of responsibility will not be an issue on our part.