Two doctors and three trainers of the former TSC Berlin club stand accused of damaging the health of 17 swimmers between 1979 and 1989, when the Berlin Wall fell, by administering steroids through pills or injections.
The trial is the second of its kind to put the former communist country's systematic doping policy under scrutiny since unification in 1990.
Ulrich Suender, 58, the club's chief doctor, admitted to providing the drugs but denied any wrongdoing, saying he had been told by his superiors any damage could be reversed.
"I did not know the full extent of the side effects in those days and I did not worry about it too much either," he told the Berlin state court.
Prosecutors argue that in some cases the drugs led to serious problems with muscular growth and that some of the swimmers suffered irreversible damage, such as infertility.
They say that at the beginning of every training year the trainers and doctors of each club used to compile a list of swimmers who would receive the drugs.
Fellow doctor Dorit Rosler, 50, and the trainers Peter Mattonet, 48, Bernd Christochowitz, 40, and Klaus Klemenz, 55, also stood on trial alongside Suender.
Several defence lawyers in the case have said their clients were ready to testify, which could lead to a swift verdict.
A similar trial of six former East German swimming officials who worked for another Berlin club, Dynamo, opened on 18 March in Berlin. Only one of those accused has testified so far and the trial is set to continue for several weeks.
Suender also said that when he worked at the TSC club with professional swimmers he was required to keep the practice of doping strictly secret.
"We were not permitted to explain this to the athletes and their families," he said, adding that he had administered the performance-enhancing drug Turinabol so that the swimmers could cope with the strain of their training programme.
He said he had not been aware of the size of each dosage, which was determined by his superiors who did not consult him.
If convicted, the five officials in the second doping trial could face sentences of several years in jail.Reuse content