This marks the first appearance of the Obsidian Order, which was going to be the Grey Order until the producers learned that the similar space station serial Babylon 5 (1993) planned to introduce a group called the Grey Council and felt the names were too similar.
Robert Hewitt Wolfe's original idea for this episode was to have Kira addicted to battle stimulants ever since her days in the Bajoran Resistance, but that idea was rejected because it would be difficult to do subsequent episodes with Kira without referencing the addiction and it was felt it could tarnish her character too much.
When Tain first meets Bashir, he calls the doctor Julian Subatoi Bashir, the only mention of Bashir's middle name in the series.
This was originally intended to be Enabran Tain's sole appearance, but, much like the situation with Garak, both the fans and producers liked Tain so much that they decided to bring him back.
This is the first DS9 episode to be directed by a woman: Kim Friedman. The producers were so impressed with her work that they brought her back to direct several crucial episodes.