Abstract: This invention relates to a method and apparatus for instantaneously monitoring the presence of properly and improperly formed needle thread stitches for all sewing machines with one or more needles at all operating speeds. An electronic control circuit connected to a high-speed synchronizer sensor and a high-speed thread sensor is provided which yields an instantaneous output of a desired duration when improper stitch formation occurs. The output from the electronic control circuit may be used to alert sewing machine operators in various ways of defective needle thread stitches.