Two "deadly" substances were detected during the trial in Canberra on Sunday, according to a member of the group conducting the testing.
Ted Noffs Foundation CEO Matt Noffs took to Twitter to share the results of the trial deemed a success by drug treatment experts.
In a Tweet he revealed, of the 85 samples tested at Groovin the Moo, two were found to be deadly.
In a controversial move, partygoers were able to get their drugs tested by volunteer medical staff and chemical analysts at the event.
The STA-Safe consortium received the last-minute go-ahead to offer free pill-testing in a mobile laboratory in a festival health tent, with the support of the ACT government and ACT Police.
Festival goers reportedly embraced the trial.
Malaysian-Australian rapper Omar Musa encouraged audiences to arrive early and use the legal service.
The Australian Drug Observatory's Dr David Caldicott was part of the group conducting the pill testing.
He told the ABC that festival goers were lining up to use the service before they had finished setting up.
He added that half the substances tested did not contain the active ingredients the pill-takers believed they were taking.
"Half of the pills that we tested in fact contained nothing active that we could detect, but a rather entertaining array of contaminants including a polish brand of toothpaste," Dr Caldicott said.
Dr Caldicott said some festival goers were deterred from taking the pills after learning what was in them.
"We had amnesty bins present and we saw at least five abandoning the drugs, far more told us that they would do so."
Nearly 130 participants took advantage of the service, according to The Ted Noffs Foundation.
"We've just taken a big step towards taking back control of the dangerous black market in drugs in order to keep our kids safe," chief executive Matt Noffs said in a statement on Monday.
