The goal of this challenge is to attract the attention of the Machine Learning community towards the problem where the input distributions, p(x), are different for test and training inputs. A number of regression and classification tasks are proposed, where the test inputs follow a different distribution than the training inputs. Training data (input-output pairs) are given, and the contestants are asked to predict the outputs associated to a set of validation and test inputs. Probabilistic predictions are strongly encouraged, though non-probabilitic “point” predictions are also accepted. The performance of the competing algorithms will be evaluated both with traditional losses that only take into account “point predictions” and with losses that evaluate the quality of the probabilistic predictions.