Hypomagnesemia has been associated with deposition of calcium pyrophosphate dihydrate crystals in articular structures, causing pseudogout, also known as calcic gout. Occasionally, pseudogout may mimic septic arthritis; this "pseudoseptic" attack may be of especial concern in the immunocompromised host, such as transplant recipient patients, who may be indeed at risk of developing septic arthritis. We report the cases of two patients in whom pseudogout developed after liver transplantation. Synovial fluid appearance and leukocyte counting in synovial fluid mimicked septic arthritis, but calcium pyrophosphate dihydrate crystals were observed. Magnesium depletion before transplantation and further tacrolimus-induced renal magnesium leakage were probably working in these patients.