a quick glance at wikipedia.org finds:

* 1910: French racer Adolphe Helière drowned at the French Riviera during a rest day.
* 1935: Spanish racer Francisco Cepeda died after plunging down a ravine on the Col du Galibier.[10]
* 1967: July 13, Stage 13: English rider Tom Simpson died of heart failure on the ascent of Mont Ventoux. Amphetamines and alcohol were found on Simpson's jersey and in his bloodstream. His death prompted tour officials to begin a program of drug testing.[10]
* 1995: July 18, stage 15: Italian racer Fabio Casartelli crashed at approximately 88 km/h descending the Col de Portet d'Aspet. Casartelli received massive head trauma from a concrete block and died on the scene[10]. He did not have a helmet, although it is unlikely wearing one would have saved him at that speed.

Apart from the deaths of riders, another two fatal accidents have also occurred.

* 1957: July 14, motorcycle rider Rene Wagter and his passenger journalist for Radio Radio-Luxembourg Alex Virot slipped on road metal (gravel) off a road without railing in the mountains near Ax-les-Thermes.[10]
* 1958: An official, Constant Wouters, died after an accident with sprinter Andre Darrigade in the 6th stage of the tour.