Abstract: Objective To observe the changes in chromacity parameters of pigmented maculae induced by narrowband-UVB light on the normal abdominal skin of healthy volunteers. Methods Minimal erythematous doses （MED） were determined in 30 healthy female volunteers. In order to induce the formation of pigmented macules, the abdominal skin of these volunteers was irradiated with 1.5 folds of MED of narrowband-UVB light. Before and after irradiation, spectrophotometer CM-2600d was employed to detect the skin chromacity parameters, including L* (representing the relative lightness ranging from total black to total white), a* （giving the balance between red and green）, b* (denoting the balance between yellow and blue), △L, △a, △b and △E values （total color difference）, and SIAscopy to quantify the levels of hemoglobin, collagen protein and total melanin in the pigmented macules. The corresponding images were captured by a computer. At the same time, the pigmented macules on the abdomen were recorded by a digital camera. Results After irradiation, the skin immediately turned to light-grey, then flared up 4 hours later; maximum pigmentation was observed at the end of the first week. Tiny desquamation was observed in 2 subjects, but no blisters were found in any of the volunteers. As shown by spectrophotometer CM-2600d, L* value reached to the nadir, a* value to the apex, while b* value remained unchanged by week 1. Since then, L* and a* values changed in opposite directions until week 8, when both values approximated the original levels before the irradiation. The hemoglobin level experienced a significant increase within the first week after the irradia- tion, then descended rapidly with time to a level lower than that before the irradiation. On the other hand, the levels of collagen protein and total melanin continued to increase and peaked on week 6 after the irradiation. Conclusions Narrowband-UVB light could induce the formation of pigmented macules on normal skin. The efficacy of skin whitening products can be evaluated by observing the changes in skin pigmentation.