"E?ziente Algorithmen" was the title of the ?rst book by Kurt Mehlhorn in 1977. It was meant as a text for graduate students and published in German by Teubner-Verlag. We decided to adopt this title 32 years later for this Festschrift in honor of Kurt on the occasion of his 60th birthday. It contains contributions by his former PhD students, many of whom are now university teachers themselves, and colleagues with whom he cooperated closely within his career. It is our pleasure that even Kurt's former PhD advisor, Bob Constable from Cornell University,...