Of almost 127 million Americans age 40 and over, more than a third are unattached. They're either casualties of the divorce explosion (13%); widowed (11%); or never married (8%).

Of those singles, more than 25 million are women. And perhaps because these over-40 women are likely to be more fit and health-conscious than their mother's generation, and to have a younger mind-set,observers say they're seeing a surge in over-40 dating — in a dating world that has changed as much as they have.