Objective: The purpose of the present study was to identify drinking patterns and determine their intraindividual stability over the course of four weeks among a sample of adults from the general population. Methods: The sample comprised 288 adults who reported drinking alcohol at least once per month (49% female; mean age = 33.1 years, SD = 12.8 years). Participants were recruited in the waiting area of a local registration office in northeastern Germany. Data were collected four times over four consecutive weeks by interview (once in the registration office and thrice by telephone). To assess alcohol consumption in the past seven days, timeline follow-back questions were administered each time. For data analysis, latent profile and latent transition analyses were applied. Indicators for latent classes were total number of drinks per seven days, number of drinking days, and number of days with heavy episodic drinking. Results: Three classes of seven-day drinking patterns were identified at baseline: (a) light drinkers (77%), (b) moderate drinkers (18%), and (c) heavy drinkers (5%). Approximately one-fifth (21%) of baseline light drinkers and 94% of baseline moderate drinkers changed their drinking pattern at least once during the four weeks. The majority (81%) of baseline moderate drinkers also reported light drinking in at least one of the three subsequent weeks. Conclusions: Our findings suggest intraindividual changes in drinking patterns even during a short period of time. Instability of drinking patterns may potentially impair the assessment of light to moderate alcohol consumption when a quantity-frequency approach is applied.