It is sometimes required to compare two simple regression lines without assuming that the variances of the two sets of error terms are necessarily equal: one may wish to (A) test whether two parallel regression lines are identical, or (B) test whether two regression lines are parallel. In this paper, a t-test for each of these problems is explained and illustrated numerically. These t-tests bear a certain resemblance to Scheffe's test for the Behrens-Fisher problem, but (unlike the latter) are not randomized tests. This paper is on a practical rather than a theoretical level; the more technical aspects of the tests are covered in Research Bulletin 63-35.