Amount and quality of detail in recollections of past events are often studied in legal psychology. What, how much, and how accurate does a witness typically recall? How can we facilitate witnesses' recollections in police interviews? How can we detect deception? The overall aim of this thesis was to employ research with high ecological validity to investigate amount and quality of detail in interviews with cooperative adults. Study I investigated details in true and false confessions by 30 cooperative offenders in a within-subject experiment. The confessions concerned one crime the respondent had conducted and been sentenced for (true confession) and one crime the respondent had never conducted nor been sentenced for (false confession). Studies II and III investigated details in interviews with 95 cooperative adults about repeated dental visits. Study II was an experiment employing a within-subject design to investigate the effect of context-specific cues on recollection of repeated events. Study III further studied the data by investigating how five factors (interviewee age, rehearsal, interviewer, number of experienced events, and unpleasantness) affected two different measures of amount and quality of detail. Study IV made all data from Studies II and III, supplemented with a codebook, freely available in an online repository. Surprisingly, Study I showed very few differences in amount and quality of detail between offenders' true and false confessions. However, three detail measures could distinguish the true and false statements, which is promising for future research on offenders' statements. Results from Study II suggested that context-specific cues may generate more details about repeated events than cues commonly used in police interviews. Thus, mnemonics such as context-specific cues may, in the future, be a positive addition to current mnemonic techniques employed in legal practice. Study III showed that the two different detail measures were affected differently by all five factors (e.g., who conducted the interview did have an affect on one of the two measures but had no effect on the second measure). The results highlight the need for standardization of how we measure amount and quality of detail in research on investigative interviewing. The data from Studies II and III can be reused as data from an experiment (including both interviews, as in Study II) or as single interview data (including data only from Interview I, as in Study III). The data and material can be used for research and educational purposes. This thesis contributes to the ongoing methodological revolution in psychology by practicing transparent reporting, publishing the data for Studies II and III, and by raising the problem of using non-standardized procedures and measures in research on investigative interviewing.