[header] How to introduce a new pet rat to another rat [title] When you bring your new rat home, don't have it in the same room as your other rat until you're sure it won't pass on any diseases. [step] Wash your hands between handling your rats. Some people choose to quarantine new rats from the others for several weeks. 
[title] When you're ready, place the new rat's cage in the same room as your other rat's cage, but about three feet away. [step] This should get them curious about each other and used to seeing and smelling each other.