Sirius red polarization method is useful to visualize the organization of connective tissues but not the molecular composition of their fibrous polymers.

There are several reports in the literature where the sirius red polarization method is used to identify the molecular type of collagen in tissue sections. We present evidence that such way of interpretation is erroneous. The sirius red polarization method is useful to visualize the organization of connective tissues and not to identify the molecular nature of their fibrous polymers.