Brown recently proposed that the "good genes" that females pursue when choo
sing mates may be individual heterozygosity because more heterozygous mates
sire offspring with higher fitness. Further, because heterozygosity might
enhance develop mental stability males with more heterozygosity are recogni
zed by the reduced fluctuating asymmetry (FA) of their bilaterally paired t
raits. We used a point sample of 67 male red-winged blackbirds (Agelaius ph
oeniceus) to test two predictions of this hypothesis: (1) males with more h
eterozygosity have higher fitness, and (2) males with more heterozygosity h
ave lower FA. We identified 7 polymorphic loci from an initial screening of
16 enzymes; 32 individuals were completely homozygous, and 35 individuals
were heterozygous at at least 1 locus. Larger and older males realized high
er mating success in this population, but neither size nor age was related
to heterozygosity. Heterozygous males were not in better condition than hom
ozygous males, nor were they less infected by hematozoa, lice, or mites. Am
ong 1-year old males, epaulet length did not differ between homozygotes and
heterozygotes, but among older males, heterozygotes did have longer epaule
ts. Homozygotes and heterozygotes did not differ in their mean FA scores fo
r nine individual characters. Although the two groups of males did differ i
n composite FA, heterozygous males were less symmetrical. Interestingly, th
is difference was attributable to a single allele at the PGM-3 locus. Combi
ned with previous results showing that FA was generally unrelated to male h
ealth, viability, parental care, social dominance, or mating success, the p
resent results indicate that Brown's hypothesis does not explain mate choic
e or male quality in this population of red-winged blackbirds.