Duncan is a BIG boy now almost 70lbs and he's been overall a very good pup. Sometimes though, he does still bite my fiancé and lunges at her, when they are playing ball or something, he'll drop the ball and start trying to bite. He doesn't typically do this with me.

He has been neutered and otherwise is very fond of her (follows her, waits for her to come in the room before he lies down).

Any ideas? He is almost 9 months.

I find a squirt gun or a spritzer bottle handy in cases like this. When he starts to nip, give him a spray with some water. It helped my dog to stop chewing shoes and kept my cat from clawing the furniture. Hope this helps.

Being very consistent with a timely correction and not giving up should solve the problem eventually. If she yells ouch and turns away every time he bites, eventually he will give up. It must be instant, and enviable. Every time he bites, he is instantly corrected.