Because there are still many unknowns regarding the toxic potential of grapes and raisins, it is advisable not to give grapes or raisins to dogs in any amount."

Additionally, here is more information about grapes and raisins and ingestion of them by dogs:

"The following information was obtained from the ASPCA's Animal Poison Control Center's EMail News Alert:

"STRANGE FRUIT? ASPCA REPORTS ON CASES OF CANINE KIDNEY FAILURE FROM GRAPES AND RAISINS

In response to reports of dogs developing kidney failure after eating large amounts of grapes or raisins, the ASPCA Animal Poison Control Center (APCC) conducted a review of all related cases in its database. Veterinary toxicologists found that all of the companion canines developed vomiting within six hours of ingestion; the estimated amounts of grapes or raisins eaten ranged from nine ounces to two pounds. Other commonly reported signs included diarrhea, anorexia, lethargy and abdominal pain, and all of the dogs developed evidence of kidney disfunction. Adds APCC's Charlotte Means, DVM, "Whether the ingested grapes were purchased fresh from grocery stores or grown in private yards didn't seem to matter, nor did the brand eaten." Clinical signs lasted for several days--sometimes even weeks. And after aggressive treatment, which included intravenous fluids and medications, half of the dogs recovered, while the others died or had to be euthanized.