A lot of the people will "Bag" flowers to keep purity.
Some rely on the low percentage of X from Isolated plants.
Some (me) would not mind a "Surprise" :)

Angela, please click on the FAQ link at the top of this first page and read the article about how to prevent cross pollination.

It should answer most of your questions, but if you still have further questions you can ask them here in the thread that you started. ( smile)

Carolyn

With a less than 5% chance of crossing, many of us don't worry about it. ;) And if you save seed from multiple fruit of the same variety, you reduce the chance of getting a cross even more. But for those who want a guaranteed purity, bag the blooms.

Dave

Thanks for the info. As Carolyn said I might, I have one last question. When you bag the blooms of the tomatoes you want to save, you don't have to bag the blooms on the whole plant or plants, just on the blooms that will create a few tomatoes for you to save the seed from, right? I've never heard of bagging blooms before this post, so thank you all very much. The FAQ was really good, too, but I did have to search for it. I've provided a link below in case anyone else wants to review it.

~Angela

Here is a link that might be useful: How Do I Prevent Tomatoes from Cross-pollinating?