According to the Gil Grissom entry on wikipedia: "Gil Grissom is loosely based on real life Las Vegas Metropolitan Police Department criminalist Daniel Holstein, today a show consultant." The source of this statement comes from a PC game review of a CSI game from pc.gamezone.com: "To add another level of realism, Ubi Soft Entertainment consulted with Daniel Holstein, Sr. Crime Scene Analyst for Las Vegas Metro. Holstein was the crime scene investigator that CSI creator Anthony Zuiker followed while doing research for the show. In fact, the main character, "Gil Grissom," is modeled after Holstein, a 20-year veteran in Las Vegas, who is also a consultant for the show. Holstein's help was vital in the development of the crime-solving PC game that stays true to the science of crime scene investigation." According to the original CSI entry on wikipedia, the character of Catherine Willows "is loosely based on real life CSI Yolanda McCleary." The source for this statement is the most solid of all of the sources, as it comes from actress Marg Helgenberger herself by Sci-Fi Online. It also confirms the wiki entry on Grissom. It would have been nice if this weren't the last nugget of knowledge I found: "SFO: You're character and Grissom are based on two real CSIs aren't they? Yes, my character is based on Yolanda McCleary and Grissom is based on Daniel Holstein. I always have to qualify by saying McCleary is not a former exotic dancer. I think she said she'd been some kind of a secretary in law enforcement, went ahead and got her... not a degree, I don't know what they call it. It's like a two year program to become a CSI. But anyway she's terrific and she's now sort of become a star in her own right because she's been featured in a lot of these shows like Dateline and she's considered to be one of the best in Vegas because she's so thorough and kind of fun and kind of sassy and all that." This answer has been brought to you by the "No Question Left Behind program." Answering old questions from currently active Answerbaggers since March 21st, 2008. (c)2008 No Question Left Behind Answer #1