Immunoreactivity of secretory component (SC) was tested in routinely processed tissue specimens of 314 colorectal cancer patients and correlated with clinicopathologic parameters, such as stage and histologic grade of the tumors as well as survival data of patients. In 22% of the carcinomas almost all tumor cells were SC positive, 36% of the tumors showed SC immunoreactivity in a focal, heterogeneous pattern, whereas in 42% of the carcinomas SC immunoreactivity did not occur. Uniformly SC positive carcinomas demonstrated a tendency to occur more frequently in the low stage and grade carcinomas, whereas uniformly SC negative neoplasms showed the reverse trend. These trends were only statistically significant for stage. Focal SC immunoreactivity (SC heterogeneous tumors) was not correlated with stage nor with grade. Furthermore, inclusion of SC heterogeneous tumors in the analysis of survival data obscured the statistical significance observed in the correlation of SC immunoreactivity status and patient survival in uniformly SC positive or negative tumors. It is concluded that the prognostic value of SC immunoreactivity patterns in colorectal carcinoma tissue appears to be limited due to the occurrence of a substantial proportion of tumors with heterogeneous SC expression and is of less significance than staging. Nevertheless, determination of the SC immunoreactivity status may be of additional value for the identification of a subpopulation of patients with a more favorable prognosis.