This paper provides information about biodegradability of biodegradable/degradable materials advertised as 100%-degradable or certified as compostable in a municipal solid-waste landfill. It describes a 12- month experiment with five samples that took place in a landfill. The results, demonstrated that the polyethylene sample with the additive (samples 1) and sample labelled as 100% degradable (sample 2) had not decomposed, and no physical changes had occurred; however, their color had changed slightly. Samples 2 and 3 (certified as compostable) did not decompose. However, sample 3 exhibited minor disruptions. Sample 5 was a control reference sample to confirm that the conditions of decomposition were suitable during the experiment, which was the case. The cellulose filter paper (sample 5) degraded after 8 months, implying that it was fully biodegraded (100%) and that the conditions required for biodegradation to occur in a sampling environment were present.