No marker except repeated fasting glucose determinations has proven useful to ascertain prospectively which women with gestational diabetes mellitus will remain euglycemic by diet modification or will require insulin therapy. We screened 183 black women with gestational diabetes mellitus to determine if the presence of islet cell, mitochondrial, nuclear, DNA, parietal cell, smooth muscle, thyroid microsomal, thyroid thyroglobulin autoantibodies, or rheumatoid factor predicted the need for insulin therapy to maintain euglycemia in women with gestational diabetes mellitus. One hundred forty-two women maintained normal fasting plasma glucose levels with dietary modifications and 41 required institution of split-dose insulin therapy. We found no significant differences in the prevalence of these autoantibodies in black women with Class GB versus Class A1 diabetes mellitus. We conclude that screening for autoantibodies in women with gestational diabetes mellitus is not useful in determining which patients will subsequently require insulin therapy during their pregnancies. © 1991, by Thieme Medical Publishers, Inc. All rights reserved.