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Background: Recent studies have indicated the predominance of Toxoplasma gondii genotype Chinese 1 in animals in China. However, little is known of the genetic features of the parasite in humans. This study aims to determine the prevalence of anti-T. gondii antibodies based on which the genetic character of the parasite was identified in cancer patients in China. Methods: A total of 1014 serum samples with malignant neoplasms were collected from six tertiary-care hospitals (HAUCM, APH, HAMU, XAH, FHH and HBMC) from January, 2012 to August, 2013. Antibodies against T. gondii were examined by enzyme-linked immunosorbent assay (ELISA). Blood samples were subsequently used for PCR assay to detect T. gondii DNA (gra6). The DNA positive samples were subjected to genotyping using a multiplex multilocus nested PCR-RFLP at 10 loci, including sag1, sag2, sag3, btub, gra6, l358, c22-8, c29-2, pk1 and apico. Samples from the patients were anonymous and only data with regard to age and gender was available at sample collection. Results: Overall, 8.38% (85/1014) of the examined patients showed positive antibodies against T. gondii. Among them, 61 (6.02%) were seropositive only for IgG, 16 (1.58%) were only for IgM, and 8 (0.79%) were found to be positive for both IgG and IgM. The seroprevalence of antibodies to Toxoplasma ranged from 5.8% to 11.0%, without regional difference (x(2) = 4.764, P = 0.445). No significant differences of the positive rates of T. gondii infection were noted in genders (male, 8.96%; female, 7.45%) (x(2) = 0.707, P = 0.400) and in ages (x(2) = 1.172, P = 0.947). Of 1014 DNA samples, 36 (3.55%) were positive for T. gondii by nested PCR at gra6 locus and nine gave rise to complete genotyping results. All samples with achieved PCR-RFLP genotyping showed a common genetic character of type Chinese 1 (ToxoDB#9). Conclusion: Seroprevalence of toxoplasmosis in immunosuppressed individuals is rarely reported in China and we presented a positive rate of 8.38% in cancer patients. Toxoplasma genomic DNA genotyping demonstrated a common genetic character of Chinese 1, indicating a possible pathogenic origin of animals in human infection.