US agents have arrested more than 90 people and shut down 16 underground labs making illegal steroids and other performance-enhancing drugs.
The Drug Enforcement Administration (DEA) said hundreds of kilos and thousands of litres of chemicals were seized in 20 states over five months.
Operation Cyber Juice focused on secret laboratories dealing in drugs obtained over the internet from China.
Agents also confiscated steroid powder, liquid and more than $2m in cash.
DEA spokesman Chuck Rosenberg said too many young people were ruining their bodies and lives through steroid abuse, but this operation had attacked the "global underground steroid market, exposing its dangers and lies".
It began in April and ended with nine arrests on Tuesday.
The DEA said many of the drugs seized were bought from Chinese chemical manufacturing companies and then converted in secret labs into forms of steroids to be sold on the US black market.
In Arizona, four so-called steroid conversion labs were shut down and 150,000 doses of the finished product seized.