The R package micompr implements a procedure for assessing if two or more multivariate samples are drawn from the same distribution. The procedure uses principal component analysis to convert multivariate observations into a set of linearly uncorrelated statistical measures, which are then compared using a number of statistical methods. This technique is independent of the distributional properties of samples and automatically selects features that best explain their differences. The procedure is appropriate for comparing samples of time series, images, spectrometric measures or similar high-dimension multivariate observations.2 Testing for significant differences in multivariate samples Two-sample or multi-sample hypothesis tests are commonly used for assessing statistically dissimilarity in univariate samples, i.e., samples composed of scalar observations. If samples are drawn from normally distributed populations, the t (two samples) and ANOVA (n-samples) tests are adequate (Montgomery and Runger, 2014). Non-parametric tests are more appropriate if population normality cannot be assumed. The Mann-Whitney U test (Gibbons and Chakraborti, 2010) and the Kolmogorov-Smirnov test (Massey Jr., 1951) are typically employed for comparing two samples. The Kruskal-Wallis test (Kruskal and Wallis, 1952) extends the former for the n-sample case.Multivariate analysis of variance (MANOVA) (Krzanowski, 1988;Tabachnick and Fidell, 2013) can be used as a statistical test for comparing multivariate samples. In this context, samples are composed of multi-dimensional observations, for which each dimension is a dependent variable (DV). However, MANOVA is not appropriate for cases with highly correlated DVs and when the number of DVs or dimensions is higher than the number of observations. Additionally, MANOVA is a parametric method which makes a series of assumptions on the underlying data which are not always met in practice.Analogous non-parametric tests exist, but they are not as widespread and are commonly oriented towards specific research topics. Multiple Response Permutation Procedures (MRPP) (Mielke Jr et al., 1976) and associated permutation-based methods, such as ANOSIM (Clarke, 1993) or permutational MANOVA (Anderson, 2001), test for differences in distances between observations from each group. These tests are implemented in the vegan package (Oksanen et al., 2016), typically used in Ecology studies. The Blossom package (Talbert et al., 2016) also provides MRPP and other distance-function based permutation tests. In a similar note, Székely and Rizzo (2004) proposed a multi-sample test for equality of multivariate distributions based on the Euclidean distance between sample elements. The test statistic belongs to a class of multivariate statistics (energy statistics) proposed by the same authors. The energy package (Rizzo and Szekely, 2016) implements this test and other energy statistics-related functionality. The cross-match test is another distance-based test (Rosenbaum, 2005), with the particularity of not requiring ...