Clinical trials are medical research studies involving volunteer participants with healthy physical conditions from various backgrounds to observe how trial drugs affect a subject’s body.

Participants are accepted, depending on the trial, based on criteria such as age, gender, body mass index (BMI) and ethnicity. Those accepted are typically well compensated.

Trial phases

Trials will have three phrases. 

Phase 1 trials are conducted only on healthy participants to examine how the drug affects the body in general, is distributed and absorbed in the body as well as to observe any commonly felt side effects.

Phases 2 and 3 are conducted with patients afflicted with the target disease or condition that the drug is meant to treat.

In Japan, most clinical trials available to foreigners are phase 1. These are usually observation  studies comparing non-Japanese participants with Japanese participants taking the same drug. It may or may not be the drug’s first human trial.


All people who decide to participate in a clinical trial in Japan must first attend a screening session. Participants who attend the screening receive payment of ¥5,000, whether they are selected to proceed with the trial or not. 

The screening session will include:

  • A health check for infectious diseases, sexually transmitted diseases (STD) and  conditions that might otherwise be unnoticed.
  • A detailed overview of the drug and trial.
  • Common side effects experienced by human subjects.

Individuals selected to participate must complete a stay in the hospital where the drug is administered. The drug will be administered to some participants while others will receive a placebo so doctors may observe a control. Participants will not know whether they have received the placebo or the test drug.

Most hospital stays are from three to 10 nights, but some can be up to one month. Participants must follow the rules and directions of the nurses and doctors, eat a strict diet (typically non-vegan) and undergo various observations and tests (e.g., several blood tests).

During free time, participants may perform remote work, read, study, watch movies and TV or play video games. However, participants must not engage in strenuous physical exercise during or before the clinical trial.

After completing the hospital stay, participants must take part in follow-up visits with the doctors, which typically last two hours.

Clinical trial safety

Trials must be evaluated and approved by an institutional review board. Trials are designed to exercise caution and each participant is monitored closely via regular blood tests, blood pressure readings, electrocardiogram (ECG) records and more. It’s important to note, however, that  adverse events or side effects can occur. It is the responsibility of the participant to understand this risk after reviewing all of the information and literature received about the trial.

Further, participants are not obligated to complete the trial. Volunteers undergoing a trial have the right to withdraw at any time and for any reason. 


Participants typically receive around ¥30,000 per day. For example, a trial with a 10-night stay would pay around ¥300,000.

Volunteers with any type of visa are accepted (even a tourist visa), but the visa must be valid throughout the duration of the trial.

How to participate

Most clinical trials are not widely advertised, as pharmaceutical manufacturers generally wish to keep the plans and details about their new medications confidential.

The best way to receive information about upcoming clinical trials in Japan is to register with a clinical research organization such as Clinical Trials Tokyo to receive emails and direct invitations for upcoming studies, including those that are not publicly posted.