More than you probably wanted to know... Good question. As I understand it, JR Duncan, who owned the ranch at the time, would not permit interior filming at Southfork #2, the one we all know and love. Here's what I've learned from the LOCATIONS thread doing research and from others who are seriously into the show's locations. S01 (5 pilots) was filmed at the Cloyce Box Ranch, now known as the Brinkmann Ranch, in Frisco TX. Most interiors were filmed at 5500 Swiss Ave, Dallas. JR/Swellen's "...don't make love any mowah" scenes were shot in one of the little houses behind the main house at the Box Ranch. S02e01-e07 - exteriors were filmed at Southfork Ranch. Interior scenes except for the den were filmed at 4800 Park Lane, Dallas. I'm assuming this would include the kitchen, where we see Gary and Bobby, and a couple of other scenes early on. The den scenes were filmed at 5020 Swiss avenue, Dallas, which had a sliding door. No other interior locations have been noted here or on other sites. I didn't know about the den until a couple of weeks ago. The producers wanted to give the impression of the den with slider opening to the breakfast patio. Note the den difference in REUNION vs ELECTION. S02e08 - beyond - ranch interiors were filmed at the Culver City studio, now Sony. The historic section of the two Swiss Ave locations is northeast of downtown Dallas. The exclusive Park Lane section is in Preston Hollow, north of downtown Dallas. Den s02e01-e07 - 5020 Swiss Ave, Dallas Den s02e08-beyond - Culver City studio Fascinating stuff to learn what the producers were doing with rooms and scenes as they are filmed out of sequence. This makes tracking rooms and entrances and other things difficult, as we've seen above relating to Southfork interiors vs exteriors.