ABSTRACTDoubled haploid (DH) lines produced via in vivo haploid induction have become an indispensable tool in maize (Zea mays L.) breeding and research. To determine the predictive value of the per se performance of haploid and DH lines in population and hybrid breeding, genetically balanced sets of haploid and DH lines along with testcrosses of the DH lines were evaluated in field trials across four locations over 2 yr in Germany. Suitable material sets were provided by three collaborating breeders. Each set comprised 54 to 58 DH lines developed from a proprietary elite dent single cross. These DH lines were crossed with one or two flint testers and subjected to haploid induction for production of corresponding haploid versions. Haploid lines, DH lines, and testcrosses were grown in separate but adjacent blocks. Haploid lines were surrounded by a mixture of inbred lines functioning as pollen source. Most haploid plants were male sterile but showed a certain degree of female fertility. Highly significant genetic variation reflected by high heritability coefficients existed in all material sets for all traits. Genetic correlations between haploid and DH lines were moderate to strong (0.5 < genetic correlation coefficient [rg] < 0.9) for early vigor, silking date, plant height, and stover weight per plant. Correlations between DH lines and testcrosses varied from nonsignificant to moderately strong for grain yield but were strong for silking date, plant height, stover yield, and grain moisture content. Silking date, early vigor, and plant height of haploid lines were moderately but significantly associated with grain yield of testcrosses. Somewhat higher estimates were obtained for the corresponding correlations between DH lines and testcrosses. In conclusion, selection for silking date, early vigor, plant height, and stover weight at the haploid level is expected to result in positive correlated genetic gain for various traits not only at the DH but also at the testcross level. Likewise, selection at the DH level may substantially speed up progress in combining ability.