Objective: To determine the clinical, aetiological and epidemiological features of onychomycosis in human immunodeficiency virus infected patients, and its relationship with the CD4 lymphocyte count. Materials and methods: Descriptive and prospective study in human immunodeficiency virus infected patients who attended the Hospital Regional Docente de Trujillo, a regional referral centre of the north of Peru. Pearson chi-squared and likelihood ratios were used to correlate clinical features, severity, the aetiological agent and CD4 count. Results: The study included a total of 51 patients, the large majority (86.3%) of them male, and with a mean age of 35 years-old. The predominant job (25.5%) was manual worker. About 74.4% stated they were non-drug users, and the most frequent sexual behaviour was heterosexual (60.8%). The onset of illness ranged from 1 to 120 months. The most common clinical presentation (60.8%) was total dystrophic onychomycosis. The most frequent (74.5%) location was the feet and 62.7% were severely compromised. The onset of human immunodeficiency virus diagnosis ranged from 1 to 96 months. Trichophyton sp. was the most found aetiological agent (52.9%). Two-thirds (66.7%) were not on antiretroviral treatment at the time of diagnosis. Viral load ranged from 80 to 1,322,930. CD4+ cell count varied between 2 and 566. A statistically significant relationship was found between clinical presentation and CD4 cell count. Conclusion: The large majority of patients were young adults, male, manual workers, non-drug users, and heterosexual. The most frequent clinical presentation was total dystrophic onychomycosis. The most commonly isolated aetiological agent was Trichophyton sp. A relationship was found between total dystrophic onychomycosis and a CD4 cell count less to 200 cell/ml.