This paper describes some observations made mainly on the growth of raftculturedmussels (Mytilus edulis L.) in Jiaochou Wan, Shandong Province. The growth rate ofthe mussels varies with the season and with age. In the first year, they grew very ra-pidly in shell length during the period from August to October, the average increment was about 10 mm per month and the greatest increment was reached in October. AfterNovember their growth rate became gradually slower until it almost ceased or entirelyceased to grow in February the next year. At the end of the first year, the maximumlength reached about 40--45mm. Compared with the first year, the growth ratewas slower during the second year, with the increment averaging 5 .7--6. 0 mm permonth in the period from April to August, the greatest increase was jn July. As tothe reared spring spats, the growth rate reached its peak in August and Septemberduring the first year, 1--2 months earlier than that of the natural ones. The increase in shell weight of the natural spring spats transplanted from Yantaiand Dalien are shown in Figure 4. Generally speaking, it Increased markedly fromMay to October, with the maximum value of 2 grams per month in August, 1 monthlater than the peak increase in shell length. The increase in shell weight was faster inthe second year than in the first year and about 80% of the total shell weight was incr-eased during the second year. In the winter although the increment became slower, the flesh still continued toincrease and reached its peak again in late March the next year, and the mean indivi-dual dried flesh weight then was 1.2--1.3 grams. From April to May the flesh weightdecreased markedly due to the spring spawning, after which it began to increase againfrom June and reached its fall peak at the beginning of October, the dried flesh weight then averaging 2. 5--3. 0 grams. From mid-October to November it decreased once morebecause of the onset of the autumn reproduction, and gradually recovering again fromDecember onward. The reared autumn spats fertilized at the beginning of October, transplanted toand cultivated in the sea in mid-December, grew to 7-8 mm long in late May or earlyJune the next year, during which time they were suitable for attachment to cultureropes in flowing water, These spats grew to about 59mm in late March the third year,every 60 individuals weighing about 1 kilogram, They were harvested at this size. The spats attached on wharves grew rather slower and were less than 20mm inaverage length through a full year, attaining only 1/3 the length of those grown onthe cultivating raft.