Questionnaire on infrequently-observed behaviors (IOBs) in Japanese macaques (Macaca fuscata) were given to primatologists. This survey aimed to provide basic information on the degree of rarity of each behavior. The questionnaire consisted of questions for respondents themselves, (e.g., name, research carrier, daily observation time), focal group (name of group and local population, captive, provisioned free-ranging, crop-raiding or purely wild), and IOBs. Experience of direct observation of 36 candidates of IOBs was also requested to answer by yes, no, or impossible to answer because of ambiguous memory or unawareness of its behavior. In total, 39 answer sheets were obtained from 32 respondents. The top 10 IOBs and the number of those answering "yes" in parenthesis are as follows: mating interruption by juveniles (1), simultaneously nursing different-aged offspring (1), tool-use (1), single mount ejaculation (2), transporting the older offspring (2), nursing the older offspring (2), simultaneously transporting different-aged offspring (3), pulling the hair of female chin as a courtship behavior by male (4), twin birth (4), and (diurnal) birth (6). Some of IOBs, such as mating interruption by juveniles, seem to be due to ambiguous memory or unawareness of its behavior. Apparent inter-population differences in the percentage of respondents answering "yes" to the all the respondents giving definite answers were found in some behaviors, such as embrace-rocking behaviors, mating behaviors in birth season, stone-handling, and feeding on vertebrates. Some of them, like the latter two, seem to have something to do with provisioning. With the modification of three categories by Nakamichi et al. (2009), we proposed the following five categories of IOBs: I) behaviors which are difficult to be observed despite its common occurrence; II) behaviors which rarely occur in every population: III) behaviors which rarely occur in some populations, but frequently occur in the others; IV) behaviors which are difficult to identify and memorize despite its common occurrence; V) behaviors which rarely occur during the most of the time but temporally occur.