Pembleton and Bayliss "cooperate" with NYPD Det.s Lennie Briscoe and Rey Curtis to solve a gas attack in a NY subway which has striking similarities to an attack in a church in Baltimore five years earlier. When the perp is being extradited back to New York, he has a heart attack and dies, reducing Pembleton to furious tears. It's indicated in this episode that the church bombing was a seminal case in Pembleton's career, mirroring Bayliss' attachment to the Watson case. (L&O: Charm City, H:LotS: For God and Country)

Munch and Falsone team up with Briscoe and Curtis when a teen-aged model's death develops ties to Baltimore. Without a confession, the judge forces both the Baltimore and the NY attorneys to cooperate and try the case together in Baltimore. (Baby, It's You 1 & 2, both shows)

Chicago Hope

When a young boy is shot down in a mall, Pembleton and Bayliss are forced to deal with the aftermath as his parents decide whether or not to take him off of child support. Once they have, and they decide to donate his organs, his heart is transported to Chicago Hope, and is seen being delivered to Dr. Jeffery Geiger. (A Doll's Eyes)

The X Files

One of the few crossovers seen only on the other show, The X Files' "Unusual Suspects" took place entirely in Baltimore. After Mulder traces The Lone Gunmen and a wanted woman named Susanne Modeski to a warehouse in Baltimore, the police end up investigating the break in. The thrust of the show is that it is told through Munch's interrogation of LG Byers. It is implied, but never seen, that Munch also interrogates Mulder.