Guayule (Parthenium argentatum Gray), a desert species native to Mexico and Texas, is being developed as an alternative to Hevea brasiliensis (A. Juss.) Muell. Arg. for production of natural rubber in arid and semiarid regions of the world. Large-scale production of guayule natural rubber requires high-rubber-yielding cultivars that can regrow successfully after each harvest and during most of the year. Such cultivars eliminate the problem of extended storage at processing plants and distribute the cost of stand establishment, by seedling transplants, across several 2-year cycles of production. Five guayule genotypes (C211, C245, C250, C400, and N565) were compared for survival and regrowth after monthly harvest, at ground level, from March 1990 through February 1991. Plants were 21 and 32 months old at the time of first and last harvest, respectively. A split-plot design with four replications was used. The main plot consisted of the five guayule genotypes and the subplots consisted of the 12 monthly harvests. Three months after each monthly harvest of different sets of plants, the number of plants that survived and regrew was recorded. Analysis of variance showed significant differences between genotypes and between months of harvest. With the exception of C400 (a selection from the second backcross generation of guayule × Parthenium tomentosum var. stramonium (Green) Rollins), all genotypes had low survival in May, June, and July harvests. The lowest survival was observed in the June harvest. C245 had good survival in eight of the 12 months, while N565 had adequate survival in only three months of the year. C400 produced vigorous new growth during most of the year. The significant genotype-by-month of harvest interaction was mainly due to the different pattern of survival demonstrated by C400. The study showed that production of guayule cultivars for harvest during most of the year may be achieved with little difficulty.