According to Official Guinness Records,
The greatest distance on inline skates (rollerblades) in 24 hours by a male is 543.59 km (337.77 miles) and was achieved by Mauro Guenci (Italy), in Senigallia, Ancona, Italy between 11 - 12 June 2004. .
For a complete list of 2004 records, please visit 2004 Guinness Records in Italy.