To investigate the diurnal behavior of linear alkylbenzene sulphonates (LAS) in domestic wastewater from a residential district on a fine-weather day, wastewater was collected for 24 hours from an upper part of a combined sewer. Dissolved LAS (D-LAS) concentration and loading began to increase from early morning and reached the highest values at 9:00. Then, they gradually decreased until noon. Multi-dimensional scaling (MDS) analysis using total LAS (T-LAS) composition showed that around the peak time wastewater was largely derived from laundry. On the other hand, there were significant shifts in D-LAS concentration and loading as well as T-LAS composition on the MDS map from 12:00 to 0:00. Therefore, LAS discharge showed a marked diurnal change. In the above investigation, the LAS adsorbed onto SS (A-LAS) and the D-LAS that is commonly analyzed were assayed. As a consequence, the former occupied larger fraction than the latter. Additionally, A-LAS composition differed from D-LAS composition, because C₁₃-LAS was predominant in A-LAS, whereas C₁₁-LAS was dominated in D-LAS. From the results, it was found that using the T-LAS obtained by analyzing A-LAS as well as D-LAS was desirable, for example, to assess the environmental pollution risk caused by combined sewer overflow. Moreover, the amount of LAS discharged from household per person per day was estimated at 1.2 g · p.e^-1 · day^-1 by taking notice of T-LAS.