Season 1 - 2 times

 108: ESCAPE
Nikita: "Just going over the parameters again."

120: BRAINWASH
Operations: "Good enough to take out Michael's source with a sophisticated car bomb. Though fortunately for us, not before the intel was passed on. The hit is expected to take place during the inaugural ball, Saturday night. Everything will proceed as planned. Mijovich's people will handle general security. Our job is to stop Griffin. Michael will lay out the mission parameters tomorrow morning. Team will fly out in the afternoon. "

Season 2 - 1 time

 220: IN BETWEEN
Nikita: Has Operations ever asked you to do something outside of mission parameters?


Season 3 - 4 times

 302: SOMEONE ELSE'S SHADOW
Madeline: "We requested it. A few parameters cropped up that give it a better than 50% chance that it's Vacek. Where are things on your end?

312: THRESHOLD OF PAIN
Michael: "Birkoff.......I'm inserting a mission parameter."
Birkoff: "All units listen up, we have a new parameter. We need Crachek alive. Restation alpha team 100 meters to the north"

 318: THIRD PARTY RIPOFF
Operations: "The only pending matter of import is the Luigi Bergomi mission. You're familiar with the parameters?"


Season 4 - 6 times

 402: THERE ARE NO MISSIONS
Operations: "Use it against him. Change parameters."

 404: INTO THE LOOKING GLASS
Adrian: "Michael. I've made this tape in case you are unsuccessful in getting the parameters of Gelman's mind control process. What you need to know is this. Nikita can be saved."

 410: HE CAME FROM FOUR
Birkoff: "Sorry. Um, so far nothing. He's a civilian. There's no way he's part of an organized hit. We zeroed out all known potentials and I'm increasing the parameters on unknown factors.
Birkoff: "Still cross-referencing. So far, nobody fits the parameters."
Birkoff: "There's no way. If it fit the parameters, we would have pulled it."

422: FOUR LIGHT YEARS FARTHER
Madeline: "We've been running this since they left, and we couldn't narrow it down to under five hundred geographical areas. Suddenly, you add a parameter to the sample space and it goes down to twenty."


Season 5 - 2 times

 503: IN THROUGH THE OUT DOOR
Operations: "Get him to Medical, then Containment. Mission parameters were specific. He was to arrive unharmed." 
Nikita: "Not necessary. Jason sent me the mission parameters. I'm up to speed."