diff --git a/opentelemetry-sdk/src/opentelemetry/sdk/trace/__init__.py b/opentelemetry-sdk/src/opentelemetry/sdk/trace/__init__.py
index 2599f23fe7..796a04d945 100644
--- a/opentelemetry-sdk/src/opentelemetry/sdk/trace/__init__.py
+++ b/opentelemetry-sdk/src/opentelemetry/sdk/trace/__init__.py
@@ -785,7 +785,9 @@ class Span(trace_api.Span, ReadableSpan):
         parent: This span's parent's `opentelemetry.trace.SpanContext`, or
             None if this is a root span
         sampler: The sampler used to create this span
-        trace_config: TODO
+        trace_config:  Unused. Originally intended for trace-level configuration
+            from the OpenTelemetry protocol, but the upstream ``TraceConfig``
+            proto was removed. Retained for backwards compatibility.
         resource: Entity producing telemetry
         attributes: The span's attributes to be exported
         events: Timestamped events to be exported