Three young Australians have been ordered to stand trial on heroin smuggling charges in Hong Kong.

Hutchinson Tran 21, unemployed, Rachel Ann Diaz, 17, a hair stylist, and Chris Ha Vo, 15, a fast food worker - all from Sydney - entered not guilty pleas in the Eastern Magistrates Court.

Their committal hearing ended within five minutes when a magistrate ruled that they had a case to answer.

The trio are being held in custody and did not apply for bail.

No trial date was set.

Officials said translation difficulties and a backlog of cases before Hong Kong's High Court might mean the case won't be heard for another year.

If convicted, Tran could be jailed for up to 20 years. It is not clear what maximum penalty Diaz and Vo, who are minors, might face.

The three were arrested in April when Hong Kong's narcotics squad raided a budget hotel room in the tourist district of Tsim Tsa Tsui, where Diaz and Vo were staying.

Police allege that the raid netted one kilogram of heroin with a street value of some $A1 million stuffed into 114 condoms and glove fingers each five centimetres in length.

Prosecutors have alleged that Diaz and Vo had been offered $A200 for each packet swallowed and they had agreed to act as drugs mules - or couriers - to smuggle the heroin into Australia inside their stomachs.