Feline immunodeficiency virus (FIV) infection was documented in 57 cats by detecting immunoglobulin G (IgG) antibodies against FIV in serum using an enzyme-linked immunosorbent assay (ELISA). Serum from the majority of cases was assayed for feline leukemia virus (FeLV) p27 antigen by use of an ELISA, IgG antibodies against coronaviruses using an indirect fluorescent antibody assay, and both immunoglobulin M (IgM) and IgG antibodies against Toxoplasma gondii using ELISA. Serological evidence of coinfection with FeLV, coronaviruses, and T. gondii was shown to be 5.5%, 26.8%, and 57.1% respectively. There was no cat with a coronavirus IgG titer > 1:400 in the study. There was no significant difference between the magnitude of T. gondii-specific IgG titers in cats from this study when compared to healthy cats. Toxoplasma gondii-specific IgM titers were of greater magnitude and were present in serum with or without T. gondii-specific IgG titers more frequently than in healthy cats. Predominant clinical findings included stomatitis, gingivitis, diarrhea, subcutaneous abscessation, anorexia, depression, elevated body temperature, weight loss, and ocular abnormalities. Cats seropositive for T. gondii were more likely to have ocular disease than cats with FIV infection alone. Cats coinfected with FeLV tended to be younger than cats with FIV infection alone, and each of the FeLV-infected cats was clinically ill. A multitude of hematological, biochemical and urinalysis abnormalities were detected; no finding was pathognomonic for FIV infection, and there were no significant differences between cats with FIV infection alone and cats with serological evidence of FIV and T. gondii coinfection. Nine had evidence of clinical feline toxoplasmosis. There were no major differences in signalment, clinical findings, or laboratory abnormalities of these cats when compared to FIV-naive cats with clinical toxoplasmosis.