Little attention has been given to the association between the host reproductive cycle and the dynamics of parasitic infection in the reptilian model. This relationship was investigated in this study with the common intestinal nematode, Thelandros schusteri (Family: pharyngodonidae) infecting the Egyptian lizards, Chalcides ocelattus.  Fifty threelizards were collected during winter and spring 2009 and were weighted and sexed. The gonads were weighted and gonadosomatic index (GSI) was calculated; both represent measures of the reproductive cycle. The intestinal nematodes were recovered from the intestine by the standard technique. Results showed that the seasonal variation did not affect the infection prevalence in male or female lizards while GSI greatly affected the prevalence in female lizards only. Females with low GSI showed the highest infection prevalence while, those of high GSI showed the highest intensity of infection. Positive or negative correlations between number of follicles/ ovary, gonad mass or GSI and the intensity of infection in female hosts suggested that the investment in reproduction of females is more costly than for males. We interpret the high intensity of infection in females to be an effect of the reproductive cycle and conclude that sex dependent difference is very important in such pattern of host parasite relationship when aspects of reproductive cycle are considered and that the host reproductive investment may be a factor contributing to occurrence of parasitic infection.