To date, human skin phototype (SPT) has been determined subjectively by self- or trained investigator assessment using sun burning and/or sun tanning responses, ethnicity, hair, and eye color. This study evaluated objective reflectance spectrophotometer (RS) assessment of SPT in 353 males or females (18-72 years old with Fitzpatrick SPT I-VI) using the area-under-the-intensity curve (AUIC) over the 450-615 nm wavelength interval of reflected light (AUIC). Photoprotected constitutive skin color sites produced higher AUIC values than photo-exposed facultative skin color sites. Constitutive skin color at the upper volar arm was equal to the buttocks. Within-site and between-site AUIC reproducibility of constitutive skin color at the upper volar arm was 3 and 5% coefficient of variation (CV), respectively, which was similar to seasonal variability (8% CV). AUIC values decreased proportionately at both constitutive and facultative sites as a function of increasing SPT from I to VI (r=0.8). RS-measured constitutive skin color at the upper volar arm fit a quadratic equation (r(2)=0.94) that differentiated (P<0.05) between each of the six SPTs and agreed +/-1 SPT category with clinician-assessed SPT. Thus, RS assessment of constitutive skin color at the upper volar arm provides a quick, noninvasive, precise, and accurate method to objectively determine SPT.