Two juvenile male Speke's gazelles (Gazella spekei) at the St. Louis Zoo showed poor body condition, slowed growth, hunched stance, rough hair coat, and profound hypophosphatemia. The first gazelle was treated with parenteral phosphorous supplements but continued to deteriorate clinically and was euthanatized. The second gazelle had serum 25-hydroxyvitamin D levels of 0 nmol/L and was treated with i.m. injections of vitamin D. It died shortly after starting therapy. The only significant necropsy finding was multiple rib fractures in various stages of healing. Hypovitaminosis D has been confirmed in multiple Speke's gazelles in this collection, indicating possible deficiencies in the diet or in the amount of ultraviolet light available to the gazelles.