Start with a different color from the one you want to make the band in. Call this the spare color. With the spare color and normal knitting needles cast on 90 stitches.
Change to your main color yarn. Knit your row of 90 stitches onto a circular needle. Your work now lies on about 2/3 of the needle. One end of the work is near the tip of the needle and has the yarn attached. This is the working end. Bend the working end around to the other end of your work, and begin to knit those stitches onto the working end, but do not slip them off the other end of the needle as you normally would. When you have knitted all 90 stitches in this way, the needle loops the work twice.
Carry on knitting in the same direction, slipping stitches off the needle when you knit them, as normal. The needle will remain looped around the work twice. Knit five `rows' (that is stitches) in this way.
Cast off. You now have a Mobius band with a row of your spare color running around the middle. Cut out and remove the spare colored yarn. You will be left with one loose stitch in your main color which needs to be secured.
Figure 8: A Mobius band.
(Expanded by Maria Iano-Fletcher from an original recipe by Miles Reid.)