The complexity of testing properties of monotone and unimodal distributions, when given access only to samples of the distribution, is investigated. Two kinds of sublineartime algorithms--those for testing monotonicity and those that take advantage of monotonicity--are provided. The first algorithm tests if a given distribution on [n] is monotone or far away from any monotone distribution in L1-norm; this algorithm uses ~O( n) samples and is shown to be nearly optimal. The next algorithm, given a joint distribution on [n]?[n], tests if it is monotone or is far away from any monotone distribution in L1-norm; this algorithm uses ~O(n3/2 ) samples. The problems of testing if two monotone distributions are close in L1-norm and if two random variables with a monotone joint distribution are close to being independent in L1-norm are also considered. Algorithms for these problems that use only poly(log n) samples are presented. The closeness and independence testing algorithms for monotone d...