In patients infected with human immunodeficiency virus (HIV), genital herpes can result in severe and atypical clinical presentations, and can become resistant to aciclovir treatment. Rarely, these manifestations may represent concurrent herpes simplex virus (HSV) with other agents. We report a 41-year-old black woman with HIV who presented with extensive and painful ulceration of the genitalia. Histological examination of a biopsy sample was suggestive of herpetic infection, and intravenous aciclovir was started, but produced only partial improvement. PCR was performed on the biopsy sample, and both HSV and cytomegalovirus (CMV) DNA was detected. Oral valganciclovir was started with therapeutic success. CMV infection is common in patients infected with HIV, but its presence in mucocutaneous lesions is rarely reported. This case exemplifies the difficulties of diagnosis of genital ulcers in patients infected with HIV. The presence of exuberant and persistent HSV genital ulcers in patients with HIV should also raise suspicions of the presence of co-infection with other organisms such as CMV.