estate complications when US green card holder with Americdan wife and property dies

Please tell me what the implications are when a Canadian citizen with US green card who is married to a US wife and living in the US dies.  What are the estate implications for the wife that remains. I have heard that there are adverse consdquences and I noticed Peter Jennings became a US citizen shortly before he died.  What are the problems that you can encounter.  i think my husband would like to retain the abiltiy to return to Canada if I should die first.  All his children are there.   Thank you,   ----------------------------------------------------
david ingram replies:

The problem occurs when 'you' die and go to leave your estate to a non-citizen husband. 

For instance, he can make a gift to you as a US citizen spouse of any amount but you can only give a non-citizen spouse $100,000 per year without incurring gift tax.

Your husband should take out US citizenship.  He does NOT lose his Canadian citizenship when becoming an American Citizen as well.

Have him go to and read the October 1993 newsletter in the top left hand box.