[catdoc]

Chocolate is toxic to pets, but the degree of toxicity varies based on what kind of chocolate. Bakers chocolate>dark chocolate>milk chocolate. Also, the size of the dog determines the amount that'll produce toxic signs. An 80-lb dog would need to eat a few lbs of milk chocolate to see toxicity from the chocolate, you'd probably see GI upset from the sugar and fats first!

A rough guideline from the ASPCA poison control hotline: Less than 1 oz of milk chocolate/lb is potentially lethal to dogs; for baking (unsweetened) chocolate, less than 0.1 oz/lb is potentially lethal. Methylxanthines can cross the placenta and pass into the milk, so unborn or nursing offspring can be affected by chocolate toxicosis in the dam. [Dark chocolate is about 3x as toxic as milk chocolate]

Regarding raisin/grape toxicity: an unknown compound in them causes kidney failure. Some individuals appear more sensitive than others (unknown why). Toxic doses are fairly low: 1.5oz/lb for grapes and 0.22 oz/lb for raisins.