The fractal exponents used to quantify the complexity of cranial sutures were computed for 17 coronal and 17 sagittal sutures of adults from different populations, using the box-counting algorithm. This paper discusses the main sources of error for the fractal exponents, and gives the error estimates. We then compare our results with those obtained by other authors. We suggest that the usual error estimates implied by the standard deviation for the regression line are too low. We emphasize the crucial role played by the choice of regression line in the log-log plot. For the coronal and sagittal sutures we found mean fractal dimensions of 1.48 and 1.56, respectively. Our values are close to the value for Brownian random walk.