Massachusetts tenants in eviction ("summary process") cases have the option of suing the landlord who is trying to evict them, in an action known as a counterclaim. A counterclaim, is a lawsuit brought against the party who first filed the lawsuit. Counterclaims are permitted in eviction cases brought for a tenant's failure to pay rent or a no-fault eviction. Counterclaims are not permitted for cause evictions (ex. violating the terms of a lease).