entering USA through Canada

[atcarync]

My parents are in Canada visiting my brother. They have both Canadian and USA visitor visas (Multiple entry to both countries). They are there since September 2010. They are planning to come to USA during Christmas and stay until summer. Do they get I-94's issued at the Border? They are planning on crossing the border at Niagara. Also do they need to extend their Canada Visa if they want to stay in USA for 6 months and then go back to Canada for few weeks before they go to India? Their flight is from Toronto.

Thanks for all the help!

[kabkaba]

The can certainly travel using their US Visa, but whether the officer will give them 6 months of stay or not cannot be predicted. If their Canada Visa remains valid when they want to return to Canada, they will also be able to return to Canada.