Animation stutters at beginning and end of loop I am pretty new to Blender so I apologize if this is a stupid question. I know it has been asked before, but during the past hour of trying, I have been unable to implement a satisfactory answer.
I have an animation (of a hippo's tail) moving back and forth in an idle animation. I am using Bezier interpolation to get a nice smooth animation and it works great with the exception of the first and last frames of the loop. I could probably get around this problem in a number of ways. I could add additional negative and positive frames at the beginning and end of my animation and loop only the central portion. I could manually edit the curves to be approximately correct. I could turn the interpolation to linear and deal with the associated issues.
What I want though is to be able to  indicate that the first and last frames are actually the same frame and have the loop working properly. I've tried adding the cyclic F modifier, but I can't get it to work properly.

Thanks very much for the help, it is much appreciated.
I should examine your .blend file to be sure, but I think that  the problem lies in the fact that your loop starts at 1 while the animation starts at 0. Instead of using 0, 8, 16, 24, 32....., use 1, 9, 17, 25, 33 ....
You'll end up with a 1-129 group of keyframes, go to keyframe 128, select all the rim and insert a new keyframe, then set the loop 1-128. If Keyframes 1 and 129 are identical it should loop perfectly.
Another way to loop an animation is via the Non Linear Editor (NLA).