Objectives To collate data from multiple obsessive–compulsive disorder (OCD) treatment centers across seven countries and five continents, and to report findings in relation to OCD comorbidity, age of onset of OCD and comorbid disorders, and suicidality, in a large clinical and ethnically diverse sample, with the aim of investigating cultural variation and the utility of the psychiatric diagnostic classification of obsessive–compulsive and related disorders. Methods Researchers in the field of OCD were invited to contribute summary statistics on current and lifetime psychiatric comorbidity, age of onset of OCD and comorbid disorders and suicidality in their patients with OCD. Results Data from 3711 adult patients with primary OCD came from Brazil (n = 955), India (n = 802), Italy (n = 750), South Africa (n = 565), Japan (n = 322), Australia (n = 219), and Spain (n = 98). The most common current comorbid disorders were major depressive disorder (28.4%; n = 1055), obsessive–compulsive personality disorder (24.5%, n = 478), generalized anxiety disorder (19.3%, n = 716), specific phobia (19.2%, n = 714) and social phobia (18.5%, n = 686). Major depression was also the most commonly co-occurring lifetime diagnosis, with a rate of 50.5% (n = 1874). OCD generally had an age of onset in late adolescence (mean = 17.9 years, SD = 1.9). Social phobia, specific phobia and body dysmorphic disorder also had an early age of onset. Co-occurring major depressive disorder, generalized anxiety disorder and psychotic disorders tended to have a later age of onset than OCD. Suicidal ideation within the last month was reported by 6.4% (n = 200) of patients with OCD and 9.0% (n = 314) reported a lifetime history of suicide attempt. Conclusions In this large cross-continental study, comorbidity in OCD was common. The high rates of comorbid major depression and anxiety disorders emphasize the need for clinicians to assess and monitor for these disorders. Earlier ages of onset of OCD, specific phobia and social phobia may indicate some relatedness between these disorders, but this requires further study. Although there do not appear to be significant cultural variations in rates or patterns of comorbidity and suicidality, further research using similar recruitment strategies and controlling for demographic and clinical variables may help to determine whether any sociocultural factors protect against suicidal ideation or psychiatric comorbidity in patients with OCD.