Both products are made from corn starch, but regular corn syrup is 100 percent glucose, while high-fructose corn syrup (HFCS) has had some of its glucose converted to fructose enzymatically.
Scientists are examining the potentially negative effects of consuming large amounts of fructose in the form of HFCS, but regular corn syrup is not part of that consideration, as it does not contain fructose.
That doesn't necessarily mean the corn syrup you buy in the store is HFCS-free, unfortunately.
Manufacturers sometimes add HFCS to regular corn syrup, but it will be listed as an ingredient if that is the case. So read labels carefully or stick with Karo, which does not add HFCS to their products.
Of course, like all refined sweeteners, corn syrup should be consumed in moderation. A few times a year around the holidays — in your grandmother's famous pecan pie recipe or the caramel candies everyone loves — sounds just about right.