Scanning electron microscopy studies of decalcified human secondary osteons were conducted to determine correlations in fiber orientations in these osteons with their appearance under crossed polaroids. Using a new sample preparation technique, osteons were prepared to expose many of their lamellar interfaces. By studying many such samples, it was concluded that osteons which appear ‘dark’ under crossed polaroids contain fibers with orientations having little or no transverse component, whereas ‘bright’ osteons possess fiber orientations with transverse and longitudinal components. ‘Intermediate’ osteons have been found to contain fiber orientations richer in longitudinal component than in