Rumors about heroin in ecstasy are mostly unfounded and untrue. As ecstasy users seek to explain the differences in experiential qualities of the often adulterated, misbranded ecstasy pills they take, heroin (as a dangerous bugbear lurking in the shadows) is often included in the list of substances that might be in ecstasy pills. Although heroin has been detected in a couple of ecstasy pills since the late 1990s, and fentanyl was detected in two pills in 2005, there is no reason to believe that heroin or related opiates are present in enough ecstasy pills to warrant the concerns expressed by some inexperienced ecstasy users.

The analysis of two pills tested by Ecstasydata.org showed the presence of fentanyl, an opiate similar in effect to heroin, but more potent.

To our knowledge, three tests have shown heroin in or on ecstasy pills:

1. one where the outside of a pill was contaminated with a small, but detectable, amount of heroin, which was not present in the inside of the pill (DanceSafe 2000),
2. a test in England in the late 1990s reported by Nicholas Saunders with no additional data,
3. and a single pill tested in the EcstasyData project (http://www.ecstasydata.org/), where the pill was very poorly made, appeared to be a "home press" and we suspect it was concocted simply for the purpose of getting a heroin entry into the database.