Although the frequency of microsatellite DNA regions generally increases with increasing genome size, genome size has a negative effect on polymerase chain reaction (PCR) amplification. Thus, researchers developing sets of PCR primers, as is commonly done for microsatellite DNA regions, may encounter greater difficulty when working with species that have larger genomes. I investigated the effect of genome size on overall amplification success using data from nine different metazoan taxa. The proportion of primer sets that did not amplify PCR products was strongly and positively correlated with the haploid C value of the target species. Increasing genome size may affect amplification success negatively because of a decrease in target:nontarget DNA or by dilution of the available primer pool by nonspecific binding.