[citation needed] The three World Indoor 1500 metre Championships won by O'Sullivan were in 1987 (Indianapolis), 1989 (Budapest), and 1993 (Toronto).

This is evidenced by the fact that O'Sullivan won the prestigious Wanamaker Mile in Madison Square Garden's Millrose Games six times (1986, 1988, 1989, 1990, 1992, and 1996).

[5] O'Sullivan, along with Irish runners Ray Flynn, Eamonn Coghlan, and Frank O'Mara established the still standing world record in the 4 x 1 mile relay, when they combined in Dublin on 17 August 1985 to run 15:49.08.

In addition to his ties to American record holder Bob Kennedy, O'Sullivan has coached elite professional runners such as Canadian indoor world silver medalist Carmen Douma-Hussar, and New Zealander Adrian Blincoe.

It takes place in Canadensis, PA, and is a one-week sleep away camp where High School cross-country runners stay in cabins [citation needed].