A study was conducted at the Kenya Agricultural Research lnstitute's National Animal Husbandry Research Centre, Naivasha, Kenya, to characterize the growth pattern of three parental lines of local chicken, Nyeri, Kericho, Taita, and a cross of Rhode Island Red with Nyeri. A total of 468 straight-run day-old chicks was used. Feed and water were provided ad libitum and the birds weighed individually on a weekly basis for 20 weeks. A non-linear growth model (Gompertz) was used to analyze the collected data which was summarized in three parameters, A, B, and K for both male and female birds. A statistical analysis of residuals was carried out to determine the best-fitted model. The pattern of growth showed little difference between the sexes up to the age of about 10 weeks, before the male birds started to gain more weight than the females in subsequent weeks. The male birds attained higher final (asymptotic) weight A than their female counterparts, although they both had similar initial weight (log A-B). The female birds had higher values of K (constant of rate of growth) which resulted in earlier maturation. The Nyeri line was superior to other indigenous lines. The Taita males were slightly larger than those of Kericho, but the latter's females exhibited better values than the former. Crossing indigenous chicken with a dual-purpose exotic breed improved growth performance under station management. For both male and female birds, a fitted model with constant B and K and varying A was found to be acceptable.