Rebecca asked what sort of DNA test to get and from what company. She mentioned an adoption in the paternal line of her husband and the father of their children. To emphasize more strongly what others have said: If you want to trace the paternal line, the test of choice is Y-DNA STR with at least 37 markers. (67 is better.) Matching sets (to a high degree) of values between pairs of results indicate a common male ancestor is shared by both men. The adoption falls into the class of things known as "non-parental events" or NPEs. These are reasonably common in genetic genealogy and one reason why people look to DNA testing. I recommend FTDNA as the testing company. They have the largest database of Y-STR results and, IMO, better tools for finding and interpreting matches. Once you have the results, you can search FTDNA's entire database to find matches. Be sure NOT to restrict the matches found to a surname, as you won't know which name will match. Also, you will need to save the kit number (user name) and password they e-mail to you in order to log into their secured website for doing the searches. But, the searches are automated and fast. Once you find matches, a tool called "DNATiP" estimates the probability of generations to the common male ancestor. -ralpht_/)