I would do it this way:
Make a B&W matte in a photo editor in TV-proportions
(4:3, not DV-proportions, to maintain the circle as a
circle in the rendered video) at double-size (slightly
soften the image to reduce the "jaggies"). Import it,
place the video on track V2 or higher, select
transparency for the video, "Image Matte", select
"reverse" (or not, as needed for correct display...),
and there you have it!

On Tue, 21 May 2002 14:00:04 +1200, "Klay" wrote:

>I made a "matte" in Photoshop (with PAL dimensions) with a black circle in
>the center of a white field - then imported to Premiere 6 an placed in on
>the track 2 over the video on track one. It didn't work. Any suggestions?
>(Would using the title editor be better?)
>
>"Steven" wrote in message
>news:Fw%F8.60606$UV4.73408@rwcrnsc54...
>> You can't crop to a circle, but you can mask to one.
>>
>> Use a track matte.
>>
>> Steven
>>
>> "Klay" wrote in message
>> news:ac9vr1$s48$9@lust.ihug.co.nz...
>> > I am interested in projecting a video to fill a specific shape (probably
>a
>> > simple circle) onto a ceiling painted black with the area projected on
>> > painted white.
>> >
>> > How can I "crop" using the clip effect (not the crop effect which
>resizes
>> > the whole image) so that I can have black background shape - as a shape
>> > other than the rectangle one can achieve with the "clip effect"? I am
>> trying
>> > to have the video image projected as a circle. I have a student whom
>would
>> > like her image projected as an amorphous shape.
>> >
>> > Is this possible with Premiere 6?