Cryptosporidium sp is one of protozoan that cause diarrhea in immunodeficient patients such as HIV/AIDS. Detection of coproantigen of Cryptosporidium sp is more sensitive than microscopic detection. The objective of this study is to detect cryptosporidiosis using coproantigen detection compare to microscopic detection from stool of HIV/AIDS patients with crhonic diarrhea. A Total of 95 stool specimens from HIV/AIDS patients with chronic diarrhea were received by Laboratorium klinik Parasitologi Faculty of Medicine UI. The stool was tested using coproantigen and microscopy detection for cryptosporidiosis. The frequency of cryptosporidiosis using koproantigen detection was 36.8% while the MTA method was only 11.6%. Sensitivity and specificity of coproantigen detection compared with the microscopic was 100% and 71.4%. Detection coproantigen necessary in patients with high suspicion of cryptosporidiosis but oocysts detection was negative.