A package for normalization of two-color microarray data. CALIB is based on the measurements of external controls and estimates an absolute target level for each gene and condition pair, as opposed to working with log-ratios as a relative measure of expression. Moreover, it makes no assumptions regarding the distribution of gene expression divergence. The underlying method relies on the presence of external control spikes to estimate the parameters of a calibration model, which are then used to obtain absolute expression levels for all genes. It provides an alternative solution to the standard ratio-based normalization, which is particularly applicable in cases where, either the GNA is violated and no alternative solutions exist, or for applications where absolute expression levels are more convenient than ratios. Besides the normalization procedure, CALIB provides some convenient visualization tools for quality control of the experimental protocol based on externally added control spikes.