Five of the six actors/actresses that play the defense attorneys have all had non-Practice related guest appearances on "Law & Order" (1990). Dylan McDermott is the only one who has not.
The cast filmed the season 7 finale thinking it would be the series finale, because ratings had taken a dive during season 7 after its new time slot. However, at the last minute, ABC renewed the show.
The old courthouse at Pemberton Square, seen in most of the exterior shots of the cases the firm tries, is the courthouse for the Boston Municipal Court, and would not be the actual courthouse used for the most part in the cases seen in the series; federal cases are now tried at the modern facility at Fan Pier in South Boston, and superior court cases at the McCormack courthouse in the financial district.
The first season featured episodes that were shot in conjunction with David E. Kelley's previous hit lawyer show "Ally McBeal" (1997). The show portrayed each practice as opposing counsel on the same case. Both shows reflected the point of view of the court from different sides.
Sharon Stone's guest 3-episode arc in the beginning of the eighth season boosted the ratings for the show, after which she considered returning to the show full-time.
Despite being on different networks, there were several crossover episodes with The Practice and David E. Kelley's other two shows, "Ally McBeal" (1997) and "Boston Public" (2000).
For the sixth season's finale, David E. Kelley filmed two different endings. One in which Lindsay Dole was found not guilty, and one in which she was found guilty. Even the cast didn't know which ending it would be until it was aired.