The pathology files of 319 consecutive temporal artery biopsies performed at the Wills Eye Hospital during an 11-year period were reviewed. Fifty-three (17%) of the biopsies were shown to have histological evidence of arteritis. Histopathologic disease was found predominately in women and only in individuals over the age of 60 years. There was no correlation between the length of the biopsy specimen and histological finding in all specimens 4 mm or longer. Sampling probability provided a method of calculating the likelihood of detecting small lesions. With proper sampling techniques, the likelihood of not detecting arteritis due to “skip lesions” in a specimen may be set under 1%.