im not so worried about my bull mastiff because she is old now and has allways been very gentle even when my children were toddlers ,its the rotty i worry about he is very energetic and bouncy but he is still young ,i decided on a yorky because i want a dog i can cuddle with that is small enough to sit on my lap but also very intelligent and beatiful to boot ,i cant exactly do that with my other dogs because the bullmastiff is 10 and just wants to be left alone to nap and the rottweiler is a dominant dog and if you give him an inch he will take a mile ,i will take your advice and only let them together when supervised and i will pick her up when the dogs are going in and out the house incase she gets stood on ,untill she learns to dodge those huge rotty feet .we pick her up tommorrow ,the whole family is so excited .thanx for your input much appreciated