2. Attempts to produce true breeding, highly self-fertile and highly self-sterile lines of tetraploid maize by inbreeding and selection thus far have not been very successful. Lines inbred 5-8 years continue to segregate for varying degrees of self-fertility. However, relatively high levels of fertility can be maintained by selecting the most fertile ears in each generation, and self-sterile ears tend to produce mostly self-sterile progeny.