Sustained-releasing praziquantel (SRP) tablet was designed for single dose treatment regimen of clonorchiasis. A previous pre-clinical study confirmed its sustained-releasing characteristics and a better cure rate than conventional praziquantel (PZQ). In this clinical study, the pharmacokinetics of this SRP tablet were investigated in human volunteers (phase 1; 12 volunteers), and its curative efficacy was examined in clonorchiasis patients (phase 2; 20 volunteers). In the phase 1 clinical study, blood concentrations of both tablets showed wide individual variation. The AUC_last of SRP was 497.9 ± 519.0 ng · hr/ml (mean ± SD) and PZQ of 628.6 ± 695.5 ng · hr/ml, and the AUC_inf of SRP was 776.0 ± 538.5 ng · hr/ml and of PZQ 658.6 ± 709.9 ng · hr/ml. C_max values of SRP and PZQ were 90.7 ± 82.2 ng/ml and 214.9 ± 251.9 ng/ml, and T_max values were 3.42 ± 1.43 hr and 1.96 ± 1.23 hr, respectively. SRP tablets showed similar AUC values, but lower C_max and longer T_max values than PZQ. In the phase 2 study, SRP at 30 mg/kg (single dose) achieved a 60% cure rate and a 95.5% egg reduction rate. The cure rate of a single dose SRP was unsatisfactory compared with that of the conventional PZQ dose, but much better than that achieved by a single dose PZQ.