The Tokyo Metropolitan Government says radiation levels at 100 locations across the city pose no health risk, but that there are high readings in some eastern areas.
The monitoring was carried out in response to public fears about contamination from the crippled Fukushima nuclear plant.
Radiation measurements were made at five centimetres and one metre about the ground, at 100 sites across Tokyo.
The Metropolitan Government says all readings were relatively low, although several spots in the city’s east recorded higher measurements.
The highest level was detected at a primary school in eastern Tokyo.
Analysts say wind direction and river flows most likely caused the elevated radiation levels in these areas.