We evaluated the medical information from 10 New World Camelids with lymphosarcoma. Additionally, tumor tissue from 5 animals was examined by electron microscopy for evidence of retroviral particles. Lymphosarcoma was the most common neoplasm of New World Camelids in our hospital. Both llamas and alpacas, from 4 months to 15 years of age, were affected. Emaciation (7 of 8) and palpable masses (9 of 10) were the most common physical examination abnormalities, and a left-shifted leukogram (7 of 7) and hypoalbuminemia (6 of 7) were the most characteristic clinicopathologic findings. Lymphosarcoma was diagnosed by lymph node aspirate (n = 2), biopsy (n = 2), peritoneal fluid analysis (n = 2), or necropsy (n = 4). The clinical course after recognition of the disease was usually short, with a median survival of 1 month (1 week to 3 months). Organs with neoplastic infiltrates commonly included lymph nodes (n = 8), liver (n = 8), kidneys (n = 6), and lungs (n = 5). No retroviral particles were detected ultrastructurally.