Two methods of researching second language learning are described, analyzed, and compared: student diaries giving a first-person account of the second language learning experience; and participant observation, in which the observer is in the language learning situation recording in descriptive terms all possible data about the situation. Pedagogical claims made about the two research methods are outlined from the relevant literature, and a study comparing the two methods is presented. The study used data from a completed study of older adult learner characteristics. Diaries written by both the older students and others in the class were compared with descriptive information gathered by an observer in the classroom and other situations in which smaller groups of the learners were participating. The data gathered in the study were examined in light of the pedagogical claims made about the methods. It was found that some of the claims for each method were upheld, and some needed modification. Some additional strengths and weaknesses that might be of use in making research decisions were identified, including the amount of researcher time needed for gathering data, certainty of gathering adequate data, and ease of quantification. It is suggested that researchers choosing between the two methods consider these factors: the need to focus on the individual learner, the desire not to change the learning situation, the desire to let the research have immediate learner use, available researcher time, and certainty and quantifiability of data. (MSE)