We introduce linear contrasts between treatment group means as a principled way for constructing t-tests and confidence intervals for treatment comparisons. We consider a variety of contrasts, including contrasts for estimating time trends and for finding minimal effective doses. Multiple comparison procedures control the family-wise error rate, and we introduce four commonly used methods by Bonferroni, Tukey, Dunnett, and Scheffe. Finally, we discuss a larger real life to exemplify the use of linear contrasts and highlight the need for careful definition of contrasts to correctly reflect the desired comparisons.