The principal helminths present in adult medical patients at Goroka Base Hospital were hookworm, probably Necator americanus, (in 83%), Ascaris lumbricoides (in 14%) and Trichuris trichiura (in 16%). Enterobius vermicularis was also present (in 1.6%), and Hymenolepis nana in a single patient. Females were infected more frequently with Ascaris than males and they had higher egg counts of both Ascaris and Trichuris than males, and the difference was statistically significant. Haemoglobin values were significantly negatively correlated with hookworm egg counts in both males and females. Eosinophil counts were not correlated with either Ascaris or hookworm egg counts in either males or females, but relatively more males with eosinophilia had high hookworm egg counts when compared with normal males. Patients with asthma had significantly lower egg counts than other patients.