The aim of this work is to compare between the International Index ofErectile Function (IIEF-15) erectile domain scores, and the parameters ofnocturnal penile tumescence and rigidity (NPTR) testing measured byRigiScan. A total of 50 men, mean age 47.9+10.8 years (range 22-69 y),presenting with erectile dysfunction (ED) were included in this study. Allthe men were evaluated with the Arabic translation of the IIEF-15, ICI,penile duplex and 2 nights of NPTR monitoring with the RigiScan.According to the IIEF-EF domain scores (that is obtained from 1 st, 2 nd,3rd, 4 th, 5 th and 15 th questions), patients were divided into threegroups: Group I; patients with mild ED (n =15), Group II; patients withmoderate ED ( n =26), and Group III; patients with severe ED ( n = 9).The distribution of the parameters of NPTR testing (Tip RAU and TAU,Base RAU and TAU, Tip maximum rigidity, Base maximum rigidity,number of erections and duration of erections) among the three groupsand the correlation with the IIEF-EF domain scores were evaluated. Astrong positive significant correlation was observed between the IIEF-EFscores and the parameters of NPTR testing (P value < 0.05). A weak nonsignificant correlation was observed between the IIEF-EF scores andpenile duplex parameters (P value > 0.05). Of the 50 men beingconsidered as having ED according to IIEF-EF scores, 4 (8%) hadnormal EF according to NPTR testing, these 4 patients were considered tohave mild ED according to IIEF-EF domain scores. When the IIEF-EFscores were compared with the parameters of NPTR testing, a statisticallysignificant difference was observed among the three groups (P value <0.05). In conclusion, we observed a significant correlation between theIIEF-EF domain scores and the NPTR parameters. Men reportingmoderate or severe ED on the IIEF are more likely to haveabnormal RigiScan results than patients reporting mild ED. Inpatients with a mild degree of ED, it is important to perform objectivetesting, a good portion of these patients could be normal and need onlyreassurance.