The present paper is the first to report the results of the work carried out on daytime melatonin levels in paired plasma and nasal lavage fluid (NAL) samples obtained from healthy adult subjects. Lavage fluid was collected from 25 volunteers using a modified Foley catheter. Blood plasma was collected using normal procedure. The immunoreactive melatonin was present in all plasma samples and in 80% of the investigated NAL samples. Blood plasma melatonin level ranged from 0.98 pg/mL to 34.97 pg/mL however the level found in NAL was lower and ranged from 0.46 to 2.42 pg/mL There was no correlation between paired plasma and nasal lavage melatonin concentration (r=0.02). Moreover, the superoxide dismutase activity (SOD) in NAL samples was determined and then the correlation coefficient between the melatonin concentration and EC-SOD activity was r= 0.18. The peroxyl radical trapping activity of 1 μmol/L melatonin was equivalent to 3 μmol/L Trolox. It has been concluded that nasal lavage fluid melatonin has limited utility in the field of melatonin research.