The aim of this study was to analyze characteristics of patients with Peyronie's disease (PD) diagnosed during a standart evaluation for erectile dysfunction (ED) and compare them with patients presenting with the classical complaints of PD. During a 10-y period, a total of 448 patients were evaluated at our two outpatient clinics, directed by the same author (AK). They were divided into two groups: group I consisted of patients, who presented with only ED and were unaware of their penile deformity, and group II consisted of patients with the classical features of the disease. The clinical characteristics, penile deformities, erectile status and the presence of comorbidities were determined in the two groups. Of 448 Peyronie's patients, 16% (n = 71) were detected during diagnostic work-up for ED. In this group of patients, ED was the presenting symptom for a mean period of 31.3 +/- 9.7 months. The mean age of men was 57.54 +/- 8.75 and 52.21 +/- 10.27 y in groups I and II, respectively (P = 0.0001). The mean degree of deformity was 31.5 +/- 12.66degrees in group I and 41.16 +/- 19.14degrees in group II (P = 0.0001). In group I (n = 71), 69% (n = 49) of the patients had a poor erectile response to the combined injection and stimulation (CIS) test. Also, in this group, the mean degrees of deformity in CIS-positive and - negative patients were 27.05 +/- 12.50 and 33.80 +/- 12.03degrees, respectively (P = 0.033). Diabetes mellitus (40%) was the leading comorbidity in group I, while at least one comorbidity was observed in 73% of the cases (P = 0.001). A remarkable percent of Peyronie's patients (16%) were detected during a standard evaluation for ED. This study analyzed, for the first time, the frequency and the characteristics of incidentally diagnosed Peyronie's patients who presented with only ED. Our data indicate that one should always consider the possibility of PD in older patients with diabetes, presenting with only ED.