Kosterlitz was a pioneer in
Alpine climbing in the 1960s, known for working routes in the UK, Italian Alps, and Yosemite. His notable ascents include the first ascent of Fessura Kosterlitz (graded
f6B/6a+) in the
Orco Valley of the Italian Alps, which was subsequently named after him, and the first repeat of American Direct (graded
ED1 6c+) on the West Face of the
Petit Dru in the
Mont Blanc Massif. Kosterlitz is credited with initiating the
Nuovo Mattino ("New Morning") movement of alpinism in the 1970s, where free,
aid-less ascents made using new technologies (such as
camming devices) became favoured. ==Personal life==